Reverting default keystone API to v2.0

Although keystone v2 has been deprecated, no services use v3 for
authorization. So passing a v3 token_id to other services results
in authorization errors. If the user logs into a domain other than
"default" the user see only unauthorized errors. Currently, when
logging into the "default" domain these authorization errors do not
occur merely because of a bug in keystone that does not validate
the token version. This will likely change some time in the
non-distant future.

Setting the keystone API version to v2.0 is the safest path for now.

Not doing a full revert because the rest of the fixes the previous
patch were valid and required.

Closes-Bug: #1294396
Change-Id: I3583e729b5a006f9b7f5cbbe3388908c15de39ae
Merge "Reverting default keystone API to v2.0"