test_evacuate.sh: Stop using libvirt-bin

I49dc963ada17a595232d3eb329d94632d07b874b missed that
call_hook_if_defined will actually cause the entire run to fail [1] if
we attempt to stop the non-existent libvirt-bin service so just remove
it now we are using the train UCA.

[1] https://opendev.org/openstack/devstack-gate/src/commit/7a70f559c559e22b498d735b4ed20aadc71b7f39/functions.sh#L74

Change-Id: Ife26f1ceb6208e12328ccdccbab0681ee55d5a2a

Author: lyarwood

gate/test_evacuate.sh

@@ -76,7 +76,6 @@ do
 done
 
 echo "Stopping libvirt on the localhost before evacuating to trigger failure"
-sudo systemctl stop libvirt-bin
 sudo systemctl stop libvirtd
 
 # Now force the evacuation to *this* host; we have to force to bypass the
@@ -111,7 +110,6 @@ evacuate_and_wait_for_error evacuate-test
 evacuate_and_wait_for_error evacuate-bfv-test
 
 echo "Now restart libvirt and perform a successful evacuation"
-sudo systemctl start libvirt-bin
 sudo systemctl start libvirtd
 sleep 10