Add support for django_openstack_auth

It would be useful for development, reviewing and testing to add
support for django_openstack_auth to devstack.

This change adds the integration tests to the openstack_auth
list of test: https://review.openstack.org/#/c/86528/

Change-Id: Ifbd336b83f6b2beb23996b599ec820232c13efdd
Closes-Bug: #1262121
diff --git a/lib/horizon b/lib/horizon
index 02715ce..1cfc605 100644
--- a/lib/horizon
+++ b/lib/horizon
@@ -26,6 +26,7 @@
 
 # Set up default directories
 HORIZON_DIR=$DEST/horizon
+HORIZONAUTH_DIR=$DEST/django_openstack_auth
 
 # local_settings.py is used to customize Dashboard settings.
 # The example file in Horizon repo is used by default.
@@ -155,6 +156,12 @@
 
 }
 
+# install_django_openstack_auth() - Collect source and prepare
+function install_django_openstack_auth {
+    git_clone $HORIZONAUTH_REPO $HORIZONAUTH_DIR $HORIZONAUTH_BRANCH
+    setup_develop $HORIZONAUTH_DIR
+}
+
 # install_horizon() - Collect source and prepare
 function install_horizon {
     # Apache installation, because we mark it NOPRIME