Add waiters after creating volume transfer for related tests

This patch set adds waiters for better test robustness following
creation of volume transfers. This is consistent with
Tempest behavior [0].

[0] https://github.com/openstack/tempest/blob/4e6b46e1969dbcb1b4c13f3a011b6f66dbe39df7/tempest/api/volume/test_volume_transfers.py#L51

Change-Id: Ifb8ab83872b203e1b2a200e5bbefc2fd3f624974
1 file changed