set OS_AUTH_TYPE in gate

we use keystone in integration gate but never set OS_AUTH_TYPE.
gnocchi will not default to keystone if OS_AUTH_TYPE isn't set.

Change-Id: I5e006c1b47a68bbe6c2e966faf8c740c23dde1ac
diff --git a/ceilometer/tests/integration/hooks/post_test_hook.sh b/ceilometer/tests/integration/hooks/post_test_hook.sh
index 68acf1a..051b4d8 100755
--- a/ceilometer/tests/integration/hooks/post_test_hook.sh
+++ b/ceilometer/tests/integration/hooks/post_test_hook.sh
@@ -97,6 +97,7 @@
 export NOVA_SERVICE_URL=$(openstack catalog show compute -c endpoints -f value | awk '/public/{print $2}')
 export GLANCE_IMAGE_NAME=$(openstack image list | awk '/ cirros.* /{print $4; exit}')
 export ADMIN_TOKEN=$(openstack token issue -c id -f value)
+export OS_AUTH_TYPE=password
 
 # Run tests with gabbi
 echo "Running telemetry integration test suite"