nova-live-migration: Only stop n-cpu and q-agt during evacuation testing
nova-live-migration: Only stop n-cpu and q-agt during evacuation testing

I8af2ad741ca08c3d88efb9aa817c4d1470491a23 started to correctly fence the
subnode ahead of evacuation testing but missed that c-vol and g-api
where also running on the host. As a result the BFV evacuation test will
fail if the volume being used is created on the c-vol backend hosted on
the subnode.

This change now avoids this by limiting the services stopped ahead of
the evacuation on the subnode to n-cpu and q-agt.

Change-Id: Ia7c317e373e4037495d379d06eda19a71412d409
Closes-Bug: #1868234

klmitch/nova,klmitch/nova,openstack/nova,openstack/nova,openstack/nova,klmitch/nova,klmitch/nova,mahak/nova,mahak/nova,mahak/nova