[Trivial]Remove unused variable assignments
[Trivial]Remove unused variable assignments

This is to remove unused variable assignments in waiters.py.

Change-Id: Ib3a7943eabaf037540520d5e0e53750c4db5743d

cisco-openstack/tempest,masayukig/tempest,cisco-openstack/tempest,openstack/tempest,masayukig/tempest,openstack/tempest