Code conventions: Use “.” to source script files
When you have to source a script file, for example ,
a credentials file to gain access to user-only or
admin-only CLI commands, use . instead of source.
See more:
http://docs.openstack.org/contributor-guide/writing-style/code-conventions
Change-Id: If2ef1f3f56008f7e9e1bec13b94d542a3b9667e7