Add missing tenant_id to Keystone init

KeystoneAuthV2 takes a tenant_id param that was not being used for
anything.  This passes it along to the keystoneclient.

Co-Authored-By: Anderson Mesquita <andersonvom@gmail.com>
Change-Id: I2cb622d4035600c09512fd3824e03da1fe5f9738
Conditionally validate KeystoneAuthV2 credentials

Don't validate the presence of KeystoneAuthV2 credential info if a
keystone client is given.

Co-Authored-By: Anderson Mesquita <andersonvom@gmail.com>
Change-Id: I5d928efda843d8a6310103bf07c375d716908031