Allow installing keystoneauth from git

Keystoneauth is not marked as stable yet however to ensure that the
integration between it, keystoneclient and other services don't break
compatibility we want to test it with tempest.

Unfortunately you can't put -e links in requirements.txt files so add
it to devstack so we can set the test environment. This will also make
it available when keystoneauth is released.

Change-Id: I43ca1df9c6ae2f0ac1a687c9ce1e2ccb97e81652
diff --git a/stackrc b/stackrc
index 342f9bf..eb0c330 100644
--- a/stackrc
+++ b/stackrc
@@ -280,6 +280,10 @@
 GITREPO["python-ironicclient"]=${IRONICCLIENT_REPO:-${GIT_BASE}/openstack/python-ironicclient.git}
 GITBRANCH["python-ironicclient"]=${IRONICCLIENT_BRANCH:-master}
 
+# the base authentication plugins that clients use to authenticate
+GITREPO["keystoneauth"]=${KEYSTONEAUTH_REPO:-${GIT_BASE}/openstack/keystoneauth.git}
+GITBRANCH["keystoneauth"]=${KEYSTONEAUTH_BRANCH:-master}
+
 # python keystone client library to nova that horizon uses
 GITREPO["python-keystoneclient"]=${KEYSTONECLIENT_REPO:-${GIT_BASE}/openstack/python-keystoneclient.git}
 GITBRANCH["python-keystoneclient"]=${KEYSTONECLIENT_BRANCH:-master}