Expand Designate RBAC testing - zone transfer req

This patch adds RBAC testing for allowed and disallowed credentials.
This is one of a series of patches adding testing. This patch covers the
zone transfer request API.

Depends-On: https://review.opendev.org/c/openstack/designate/+/836217
Change-Id: I7699e44ced5462267fe45cac78b1ee148f6603f6
2 files changed