provide an override-defaults phase

during the glusterfs integration it was seen that plugins might need
to set new defaults on projects before the project files load. Create
a new override-defaults phase for that.

Intentionally not adding to the documentation yet until we're sure
this works right in the glusterfs case.

Reported-By: Deepak C Shetty <deepakcs@redhat.com>
Change-Id: I13c961b19bdcc1a99e9a7068fe91bbaac787e948
diff --git a/stack.sh b/stack.sh
index 9069367..a9deba7 100755
--- a/stack.sh
+++ b/stack.sh
@@ -507,6 +507,10 @@
 # Configure Projects
 # ==================
 
+# Plugin Phase 0: override_defaults - allow pluggins to override
+# defaults before other services are run
+run_phase override_defaults
+
 # Import apache functions
 source $TOP_DIR/lib/apache