Relax regex when keystone refuses connections

Seems newer python-keystoneclient have a different excpetion message,
specifically they dropped the HTTP prefix.  Now we allow both messages to be
trapped.

Add some additional cases that are common regex now covers
 (HTTP 400)
 [Errno 111] Connection refused
 503 Service Unavailable
 Max retries exceeded
 HTTP Unable to establish connection
 Unable to establish connection to http://...

Change-Id: I71fada12b3dbb681288c7ef2891603f970910736
Signed-off-by: Paul Belanger <paul.belanger@polybeacon.com>
Signed-off-by: Andrew Woodward <awoodward@mirantis.com>