Fixing n-crt removal from stackrc

The commit 279cfe75198c723519f1fb361b2bff3c641c6cef removed the n-crt
service from the default devstack setup. As such, the stack.sh script
begun to thrown the following error when trying to "nova x509-create-cert":

  ERROR (ClientException): The server has either erred or is incapable of
  performing the requested operation. (HTTP 500)

This patches reintroduces the n-crt as a default service.

Change-Id: Id9695a37e1c6df567f2c86baa4475225adcfb0ee
Closes-bug: #1441007
diff --git a/stackrc b/stackrc
index abedb00..0b93d32 100644
--- a/stackrc
+++ b/stackrc
@@ -49,7 +49,7 @@
     # Keystone - nothing works without keystone
     ENABLED_SERVICES=key
     # Nova - services to support libvirt based openstack clouds
-    ENABLED_SERVICES+=,n-api,n-cpu,n-net,n-cond,n-sch,n-novnc
+    ENABLED_SERVICES+=,n-api,n-cpu,n-net,n-cond,n-sch,n-novnc,n-crt
     # Glance services needed for Nova
     ENABLED_SERVICES+=,g-api,g-reg
     # Cinder