Test against latest glance_store code

Install glance_store from git so we can test Glance against master. This
is useful for both, glance and glance_store gates, to make sure nothing
is broken there.

Change-Id: I6c01165c4384c41f46f2c32d64475703b3178dab
diff --git a/stackrc b/stackrc
index e071132..8663a7b 100644
--- a/stackrc
+++ b/stackrc
@@ -144,6 +144,9 @@
 GLANCE_REPO=${GLANCE_REPO:-${GIT_BASE}/openstack/glance.git}
 GLANCE_BRANCH=${GLANCE_BRANCH:-master}
 
+GLANCE_STORE_REPO=${GLANCE_STORE_REPO:-${GIT_BASE}/openstack/glance_store.git}
+GLANCE_STORE_BRANCH=${GLANCE_STORE_BRANCH:-master}
+
 # python glance client library
 GLANCECLIENT_REPO=${GLANCECLIENT_REPO:-${GIT_BASE}/openstack/python-glanceclient.git}
 GLANCECLIENT_BRANCH=${GLANCECLIENT_BRANCH:-master}