Track db sync command time useage

We are trying to keep better track of what pieces of devstack consume
the most time. Add the db sync commands to the time tracking as they run
the database migrations which can take more time than expected.

Change-Id: Ib92f2b8304ccf703712d45fd7207444de3599e2d
diff --git a/lib/nova b/lib/nova
index aae3108..18715fc 100644
--- a/lib/nova
+++ b/lib/nova
@@ -649,7 +649,9 @@
             iniset $NOVA_CELLS_CONF DEFAULT enabled_apis metadata
         fi
 
+        time_start "dbsync"
         $NOVA_BIN_DIR/nova-manage --config-file $NOVA_CELLS_CONF db sync
+        time_stop "dbsync"
         $NOVA_BIN_DIR/nova-manage --config-file $NOVA_CELLS_CONF cell create --name=region --cell_type=parent --username=$RABBIT_USERID --hostname=$RABBIT_HOST --port=5672 --password=$RABBIT_PASSWORD --virtual_host=/ --woffset=0 --wscale=1
         $NOVA_BIN_DIR/nova-manage cell create --name=child --cell_type=child --username=$RABBIT_USERID --hostname=$RABBIT_HOST --port=5672 --password=$RABBIT_PASSWORD --virtual_host=child_cell --woffset=0 --wscale=1