Revert "Stop accepting 1 return code for cell_v2_map_cell0"

I'm reverting this now because we are failing to promote RDO repos with more recent nova.

I'll re-revert it later.

This reverts commit d284943b65.

Change-Id: Idf2394b9d92959af3b95410ab538693fd8f5ca45

manifests/cell_v2/map_cell0.pp

@@ -21,6 +21,7 @@ class nova::cell_v2::map_cell0 (
     path        => ['/bin', '/usr/bin'],
     command     => "nova-manage ${extra_params} cell_v2 map_cell0",
     refreshonly => true,
+    returns     => [0,1], # TODO(owalsh): Remove when this lands https://review.openstack.org/#/c/420132/ in packaging
     logoutput   => on_failure,
     subscribe   => Anchor['nova::cell_v2::begin'],
     notify      => Anchor['nova::cell_v2::end'],