Add the possibility of using a dedicated private key

[IshentRas]

• The current rhc command relies on finding the private key inside the home directory of the user running the command.
• In addition it also expects the common name id_rsa or id_dsa
  This change gives the user the ability of defining a dedicated private key.

[tiwillia]

[test]

[openshift-bot]

Online Test Results: SUCCESS (https://ci.dev.openshift.redhat.com/jenkins/job/test_pull_requests/8843/)

[openshift-bot]

Evaluated for online test up to 0bb8629

[Miciah]

Is the "private key is inaccessible" different from the "private key does not exist" test?

[Miciah]

@tiwillia pointed out to me that the --key option (or --ssh_key if you decide to rename it) would be applicable to the ssh, scp, tail, snapshot, and port-forward commands as well, so it should be a global option. Could you please make that change, @IshentRas?

Edit: If you think it would be helpful to you, please refer to https://github.com/openshift/rhc/pull/696/files as an example of changing a command-specific option into a global option.

[openshift-bot]

Online Action Required: Pull request cannot be automatically merged, please rebase your branch from latest HEAD and push again