Set auth_version to v2.0

When no auth_version value is provided, it still should explicitly
set auth_version to v2.0 as the default value.
This is also to be consistent with other components. The current
code does not have 'auth_version = v2.0' in the configuration file.

Change-Id: Ie8c23ec2eef0b0ad70b4937e7ae68ac66188f1f2
Closes-Bug: #1387016