Fix for configuring non-default auth plugins properly

Make sure we pick up CONF.auth.methods from configuration
files. Added a test case to make sure the we don't regress

Fixes LP# 1157515

Change-Id: I70290c37b2a5378b5247a14e3bfa20d50bf8fe74
Merge "Fix for configuring non-default auth plugins properly" into stable/grizzly