RabbitMQ Input doesn't use default URL but instead gives protocol scheme error

[martinseener]

Bug report

System info:

Telegraf 0.13.0
Debian Squeeze LTS (all updates) but should be OS independent

Steps to reproduce:

Use the rabbitmq input plugin and only specify a user and password. You will see and error thrown into the telegraf.log instead of the default URL being used

Expected behavior:

I expect that the DefaultURL http://localhost:15672 is being used when not specified explicitly.

Actual behavior:

The default URL is somehow not used but instead the following error is thrown and no metrics are gathered. When setting url = "http://localhost:15672" then everything is fine.

Additional info:

Example log line:
2016/05/26 11:02:00 Error in input [rabbitmq]: Get /api/queues: unsupported protocol scheme ""

Proposal:

Since iam not good in go someone needs to fix it so the DefaultURL is used when not explicitly defined.