devstack: fix debug info for Gnocchi

Currently the gate job fails with:

2015-10-12 12:05:42.435 | * Unprocessed measures:
2015-10-12 12:05:42.448 | find: `/measures': No such file or directory

Because we didn't source the Gnocchi settings.

Change-Id: I35f2ea0d23a38d1cb514db72c2fe4bdf41c06f29
diff --git a/ceilometer/tests/integration/hooks/post_test_hook.sh b/ceilometer/tests/integration/hooks/post_test_hook.sh
index ce44229..6d4e418 100755
--- a/ceilometer/tests/integration/hooks/post_test_hook.sh
+++ b/ceilometer/tests/integration/hooks/post_test_hook.sh
@@ -74,6 +74,8 @@
         echo $output | python -m "json.tool" || echo -e "\n$output"
     done
 
+    # Be sure to source Gnocchi settings before
+    source $BASE/new/gnocchi/devstack/settings
     echo "* Unprocessed measures:"
     find $GNOCCHI_DATA_DIR/measures
     set -x