Description of problem:
Attempting to push pot sources in a language other than English fails if en-US is not configured on the server. 

Version-Release number of selected component (if applicable):
Reported against 1.5, but also present in 1.6

How reproducible:
Always


Steps to Reproduce:
1. Configure a Zanata instance with languages other than en-US.
2. In zanata.xml, configure zanata.sourceLang to something other than en-US.
3. Try to push sources using the python or maven client.
  
Actual results:
With the maven client, the following error is reported:
Failed to execute goal org.zanata:zanata-maven-plugin:1.6.1-SNAPSHOT:push (default-cli) on project test: Zanata mojo exception: operation returned 403 (Forbidden): Locale en-US is not enabled on this server. Please contact admin., uri: http://XXXX/zanata/rest/projects/p/test/iterat
ions/i/1.0/r, annotations: [@javax.ws.rs.PUT(), @javax.ws.rs.Path(value={id})] -> [Help 1]


Expected results:
Zanata should allow the push of the source files.

Additional info:
If en-US is configured, the source files are pushed successfully.
Bug originally reported by a community user.