More info when fail to get api version

When tempest verify-config incorrectly guesses the unversioned
endpoint (for example when keystone is accepting requests on a
subpath) it might get a response that's not JSON, in which point
all that it prints out is that the response isn't JSON. It would
be more useful if the URL that was requested was also printed so
that the user could see what was wrong.

Change-Id: Idb5f8ad9290569cf559bd2141b82075e6e0d6091
2 files changed