Corrected basic authentication logic in vmdbws controller

Ensure username instance variable gets set in controller.
Fixed authenticate_or_request_with_http_basic block so it returns true/false
Updated authenticate logic in User.authenticate_with_http_basic to return false
for a bad password so the controller returns 401 Unauthorized error instead of raise error.
Added test to user spec for authenticate_with_http_basic.
Added http_login helper methods.

https://bugzilla.redhat.com/show_bug.cgi?id=1118831