Generate deprecation warning for postgresql

Change-Id: I599e6d84b70bb6a7718ae48dd0cfc91796af189e
diff --git a/lib/databases/postgresql b/lib/databases/postgresql
index 1f347f5..618834b 100644
--- a/lib/databases/postgresql
+++ b/lib/databases/postgresql
@@ -95,6 +95,7 @@
 
 function install_database_postgresql {
     echo_summary "Installing postgresql"
+    deprecated "Use of postgresql in devstack is deprecated, and will be removed during the Pike cycle"
     local pgpass=$HOME/.pgpass
     if [[ ! -e $pgpass ]]; then
         cat <<EOF > $pgpass