Fix for keystone example usage

Keystone example usage for keystone auth flags has wrong keyword arguments (flag-like).
Keystone accepts token and endpoint on the command line.
Valid arguments are --os-token and --os-endpoint.
--token should be --os-token
--endpoint should be --os-endpoint
Also, updating env. varabiles from SERVICE_TOKEN to OS_SERVICE_TOKEN and
SERVICE_ENDPOINT to OS_SERVICE_ENDPOINT

Change-Id: I24b41c5d7ddfdd7f8a388eb7b7ba1a1b7fa59542
Closes-bug: #1307302
Merge "Fix for keystone example usage"