Drop stack name from the neutron agent-list check

Heat doesn't always include the full name of the stack in in the
resource name (which gets propagated into the neutron agents). The
previous check was failing when the NovaCompute resource was wrapped in
a provider template and/or a ResourceGroup.

Change-Id: I50c72aca9c69545d58a1a6ebd09c189c41c19551
Merge "Drop stack name from the neutron agent-list check"