After patch Ia08538ccf00c9063dc0d284c5ece9a969c15500a the urljoin would
ensure that a URL was always returned from the get_endpoint method even
when the version was not available. This breaks plugin discovery and a
number of other areas.
Change-Id: I04014b6e770c2e9708c5f9c81c3160d51603ad0c
Closes-Bug: #1616720