Set proper DB_INIT_VERSION on db_version command

When db_version argument to keystone-manage is used before db_sync
the versioning API incorrectly versioned the DB to 0. The code now
properly references the DB_INIT_VERSION allowing for db_version
to be run on an unversioned database prior to sync.

Change-Id: Idca5c8a3f4822ade8a5566181960085862ec2429
Closes-Bug: 1314340
Merge "Set proper DB_INIT_VERSION on db_version command"