Refactor rpc backend vhost creation

The creation of the cellsv1 rpc vhost was buried in the restart function,
which makes it hard to extend. This breaks it out into a helper method
and moves the conditional logic into the nova module itself.

Change-Id: Ib0e377aabe45c27bb6ce59ca275ce73085e8b9d2

lib/nova

@@ -644,6 +644,7 @@ function init_nova_cells {
     if is_service_enabled n-cell; then
         cp $NOVA_CONF $NOVA_CELLS_CONF
         iniset $NOVA_CELLS_CONF database connection `database_connection_url $NOVA_CELLS_DB`
+        rpc_backend_add_vhost child_cell
         iniset_rpc_backend nova $NOVA_CELLS_CONF DEFAULT child_cell
         iniset $NOVA_CELLS_CONF DEFAULT dhcpbridge_flagfile $NOVA_CELLS_CONF
         iniset $NOVA_CELLS_CONF cells enable True

lib/rpc_backend

@@ -97,13 +97,20 @@ function restart_rpc_backend {
 
             break
         done
-        if is_service_enabled n-cell; then
-            # Add partitioned access for the child cell
-            if [ -z `sudo rabbitmqctl list_vhosts | grep child_cell` ]; then
-                sudo rabbitmqctl add_vhost child_cell
-                sudo rabbitmqctl set_permissions -p child_cell $RABBIT_USERID ".*" ".*" ".*"
-            fi
+    fi
+}
+
+# adds a vhost to the rpc backend
+function rpc_backend_add_vhost {
+    local vhost="$1"
+    if is_service_enabled rabbit; then
+        if [ -z `sudo rabbitmqctl list_vhosts | grep $vhost` ]; then
+            sudo rabbitmqctl add_vhost $vhost
+            sudo rabbitmqctl set_permissions -p $vhost $RABBIT_USERID ".*" ".*" ".*"
         fi
+    else
+        echo 'RPC backend does not support vhosts'
+        return 1
     fi
 }