Prepare for dropping keystone admin endpoint

Keystone no longer has any special functionality hidden behind the admin
endpoint. Stop referencing it in consumers, so it can later be dropped
completely.

Change-Id: I04a5d77908005268cc7c59e7e9ddeea70f6732e2
diff --git a/stack.sh b/stack.sh
index 709b97b..37e7518 100755
--- a/stack.sh
+++ b/stack.sh
@@ -1053,7 +1053,7 @@
 
 # Set up password auth credentials now that Keystone is bootstrapped
 export OS_IDENTITY_API_VERSION=3
-export OS_AUTH_URL=$KEYSTONE_AUTH_URI
+export OS_AUTH_URL=$KEYSTONE_SERVICE_URI
 export OS_USERNAME=admin
 export OS_USER_DOMAIN_ID=default
 export OS_PASSWORD=$ADMIN_PASSWORD