Remove nova cert from devstack

As a followup to I2c78a0c6599b92040146cf9f0042cff8fd2509c3, the nova
cert service should be removed from devstack.

Without this fix, stacking will fail is USE_SCREEN=True

Change-Id: I115580352fa380b896bae290f9a4efbfe4ff0dfd
diff --git a/lib/nova b/lib/nova
index de053ab..e580abb 100644
--- a/lib/nova
+++ b/lib/nova
@@ -878,7 +878,6 @@
     run_process n-cond "$NOVA_BIN_DIR/nova-conductor --config-file $compute_cell_conf"
     run_process n-cell-region "$NOVA_BIN_DIR/nova-cells --config-file $api_cell_conf"
     run_process n-cell-child "$NOVA_BIN_DIR/nova-cells --config-file $compute_cell_conf"
-    run_process n-crt "$NOVA_BIN_DIR/nova-cert --config-file $api_cell_conf"
 
     if is_service_enabled n-net; then
         if ! running_in_container; then
@@ -929,7 +928,7 @@
     # Kill the nova screen windows
     # Some services are listed here twice since more than one instance
     # of a service may be running in certain configs.
-    for serv in n-api n-crt n-net n-sch n-novnc n-xvnc n-cauth n-spice n-cond n-cell n-cell n-api-meta n-sproxy; do
+    for serv in n-api n-net n-sch n-novnc n-xvnc n-cauth n-spice n-cond n-cell n-cell n-api-meta n-sproxy; do
         stop_process $serv
     done
 }