Configure nova_cell1.conf to use placement for reschedules

Nova now calculates alternate hosts in the scheduler and
sends those to the cell for reschedules in case a build on
a given compute node fails.

The cell conductor needs to claim resources against the
alternate hosts in Placement during a reschedule, therefore
it needs to be configured to talk to the placement service.

Part of blueprint return-alternate-hosts

Change-Id: Ie599968d9e7537e551fe6d9deb63a91b256b1e11
diff --git a/lib/nova b/lib/nova
index 50deeeb..c40c43a 100644
--- a/lib/nova
+++ b/lib/nova
@@ -600,6 +600,12 @@
             else
                 rpc_backend_add_vhost $vhost
                 iniset_rpc_backend nova $conf DEFAULT $vhost
+                # When running in superconductor mode, the cell conductor
+                # must be configured to talk to the placement service for
+                # reschedules to work.
+                if is_service_enabled placement placement-client; then
+                    configure_placement_nova_compute $conf
+                fi
             fi
             # Format logging
             setup_logging $conf