Check existence of expires_in for auth
Check existence of expires_in for auth

If a registries doesn't provide an expires_in with their token, the
current code fails doing the comparison. If no such header is included,
let's assume there is no expire time so we can just use the cached
token.  If the token expires, we'll reauth as usual.

Change-Id: I96ab407ba50e2183141daec3341dbb29545d5beb
Closes-Bug: #1912645

openstack/tripleo-common,openstack/tripleo-common