Fixes lib/heat to use DATABASE_PASSWORD instead of MYSQL_PASSWORD

The latter is not used anywhere else, but the former is used in all
of the other projects sharing the mysql database for devstack.

Change-Id: I2a0cd7e5b908eb144468caf410a6c41e0e5e3fd0
diff --git a/lib/heat b/lib/heat
index feaadec..43115cb 100644
--- a/lib/heat
+++ b/lib/heat
@@ -175,7 +175,7 @@
     # (re)create heat database
     recreate_database heat utf8
 
-    $HEAT_DIR/bin/heat-db-setup $os_PACKAGE -r $MYSQL_PASSWORD
+    $HEAT_DIR/bin/heat-db-setup $os_PACKAGE -r $DATABASE_PASSWORD
     $HEAT_DIR/tools/nova_create_flavors.sh
 }