Begin is_service_enabled() cleanup

This converts the special cases in the is_service_enabled() function to call
individual functions declared by the projects.  This allows projects that
are not in the DevStack repo and called via the extras.d plugin to handle
an equivalent service alias.

* Ceilometer
* Cinder
* Glance
* Neutron
* Nova
* Swift

TODO: remove the tests from is_service_enabled() after a transition period

Patch Set 2: Rebased

Change-Id: Ic78be433f93a9dd5f46be548bdbd4c984e0da6e7
diff --git a/lib/nova b/lib/nova
index dbc5c3d..c6d9936 100644
--- a/lib/nova
+++ b/lib/nova
@@ -129,6 +129,20 @@
 # Functions
 # ---------
 
+# Test if any Nova services are enabled
+# is_nova_enabled
+function is_nova_enabled {
+    [[ ,${ENABLED_SERVICES} =~ ,"n-" ]] && return 0
+    return 1
+}
+
+# Test if any Nova Cell services are enabled
+# is_nova_enabled
+function is_n-cell_enabled {
+    [[ ,${ENABLED_SERVICES} =~ ,"n-cell-" ]] && return 0
+    return 1
+}
+
 # Helper to clean iptables rules
 function clean_iptables() {
     # Delete rules