[EvmDatabaseOps] Fix .validate_free_space target

Currently, `db_opts[:local_file]` will always be a FIFO with the new
file_storage mechanisms, so `.validate_free_space` will only check
against the tmp dir, which usually isn't very large and not the target
destination for the DB backup/dump.

This fix moves the check to a place were we can get access to the
file_storage object directly and target the directory of the mounted
filesystem that will receive the backup/dump.

To that end, the check now only applies to file storage classes that are
"mountable", since checking against non-mountable storages don't make
sense (s3/swift don't have this capability, and they are assumed to be
"infinite" anyway, and I don't think you can query FTP for available
storage as well so I think the same assumption is also fair to apply)

* * *

Quick note:

In a couple of spots in the tests, the following is added:

    allow(file_storage).to receive(:class).and_return(MiqSmbSession)

Despite `file_storage` being defined above with:

    let(:file_storage) { double("MiqSmbSession", :disconnect => nil) }

This is now required after moving validate_free_space to inside the
with_file_storage method, and wrapping it in a class check of:

    if file_storage.class <= MiqGenericMountSession

This "stubs the stub" to have it act like a MiqSmbSession, when in fact,
it isn't.  Unfortunately, this can't be used globally since it causes a
bunch of other tests failures.

lib/evm_database_ops.rb

@@ -55,7 +55,6 @@ def self.backup(db_opts, connect_opts = {})
     #   :remote_file_name => "backup_1",     - Provide a base file name for the uploaded file
 
     uri = with_file_storage(:backup, db_opts, connect_opts) do |database_opts|
-      validate_free_space(database_opts)
       backup_result = PostgresAdmin.backup(database_opts)
       backup_result
     end
@@ -67,11 +66,6 @@ def self.dump(db_opts, connect_opts = {})
     # db_opts and connect_opts similar to .backup
 
     uri = with_file_storage(:dump, db_opts, connect_opts) do |database_opts|
-      # For database dumps, this isn't going to be as accurate (since the dump
-      # size will probably be larger than the calculated BD size), but it still
-      # won't hurt to do as a generic way to get a rough idea if we have enough
-      # disk space or the appliance for the task.
-      validate_free_space(database_opts)
       PostgresAdmin.backup_pg_dump(database_opts)
     end
     _log.info("[#{merged_db_opts(db_opts)[:dbname]}] database has been dumped up to file: [#{uri}]")
@@ -168,6 +162,16 @@ def self.restore(db_opts, connect_opts = {})
         if action == :restore
           yield(db_opts, backup_type)
         else
+          if file_storage.class <= MiqGenericMountSession
+            # Only check free space on "mountable" storages
+            #
+            # For database dumps, this isn't going to be as accurate (since the
+            # dump size will probably be larger than the calculated DB size), but
+            # it still won't hurt to do as a generic way to get a rough idea if
+            # we have enough disk space on the appliance for the task.
+            free_space_opts = db_opts.merge(:local_file => file_storage.uri_to_local_path(uri))
+            validate_free_space(free_space_opts)
+          end
           yield(db_opts)
         end
       end

spec/lib/evm_database_ops_spec.rb

@@ -46,6 +46,7 @@
 
     it "without enough free space" do
       EvmSpecHelper.create_guid_miq_server_zone
+      allow(file_storage).to receive(:class).and_return(MiqSmbSession)
       allow(EvmDatabaseOps).to receive(:backup_destination_free_space).and_return(100.megabytes)
       allow(EvmDatabaseOps).to receive(:database_size).and_return(200.megabytes)
       expect { EvmDatabaseOps.backup(@db_opts, @connect_opts) }.to raise_error(MiqException::MiqDatabaseBackupInsufficientSpace)
@@ -74,6 +75,8 @@
       allow(described_class).to receive(:backup_file_name).and_return("miq_backup")
       expect(PostgresAdmin).to receive(:backup).with(run_db_ops)
 
+      allow(file_storage).to receive(:class).and_return(MiqSmbSession)
+
       log_stub = instance_double("_log")
       expect(described_class).to receive(:_log).twice.and_return(log_stub)
       expect(log_stub).to        receive(:info).with(any_args)
@@ -89,6 +92,7 @@
       @connect_opts = {:username => 'blah', :password => 'blahblah', :uri => "smb://myserver.com/share"}
       @db_opts =      {:dbname => 'vmdb_production', :username => 'root'}
       allow(file_storage).to  receive(:settings_mount_point).and_return(tmpdir)
+      allow(file_storage).to  receive(:uri_to_local_path).and_return(tmpdir.join("share").to_s)
       allow(file_storage).to  receive(:add).and_yield(input_path)
 
       allow(MiqUtil).to        receive(:runcmd)
@@ -121,6 +125,7 @@
 
     it "without enough free space" do
       EvmSpecHelper.create_guid_miq_server_zone
+      allow(file_storage).to receive(:class).and_return(MiqSmbSession)
       allow(EvmDatabaseOps).to receive(:backup_destination_free_space).and_return(100.megabytes)
       allow(EvmDatabaseOps).to receive(:database_size).and_return(200.megabytes)
       expect(PostgresAdmin).to receive(:backup_pg_dump).never