With the inclusion of the Mixed RHEL deployments Live Migration is only
supported from older to new hypervisors. Current SR-IOV live migration
tests migrate back and forth by default. Add the
compute_feature_enabled.live_migrate_back_and_forth to the SR-IOV live
migration tests so that when testing Mixed RHEL deployments tests stop
after initial live migration.
By default the flag is false so adding the configuration as True to
devstack if SR-IOV tests are ever enabled upstream.
Change-Id: I0b188a484dcefd846613d05fe4c49e710778a952
c059764085