use setup_install for django_openstack_auth

This is fundamentally a library. As such we should setup_install
so that we can possibly pin it, otherwise we *always* get the
git version instead.

Change-Id: Ia815f2675cf535bb05a7e8eda853690171559b86
diff --git a/lib/horizon b/lib/horizon
index bf476c6..a65b243 100644
--- a/lib/horizon
+++ b/lib/horizon
@@ -159,7 +159,7 @@
 # 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
+    setup_install $HORIZONAUTH_DIR
 }
 
 # install_horizon() - Collect source and prepare