Don't treat service as enabled if in disabled list

The old implementation for is_$service_enabled simply checked if any of
the subservices were enabled and if so the service was considered to be
enabled. This makes disabling services complicated as it means you have
to list every single subservice which can and do change over time.

Instead also check if the generic service name is in the disabled
services list and if so don't treat the service as enabled.

Change-Id: I7fe4dfca2cd9c15069d50a04161a29c5638291cb
diff --git a/lib/cinder b/lib/cinder
index 2cbab20..291eebe 100644
--- a/lib/cinder
+++ b/lib/cinder
@@ -129,6 +129,7 @@
 # Test if any Cinder services are enabled
 # is_cinder_enabled
 function is_cinder_enabled {
+    [[ ,${DISABLED_SERVICES} =~ ,"cinder" ]] && return 1
     [[ ,${ENABLED_SERVICES} =~ ,"c-" ]] && return 0
     return 1
 }