Add pydot to stein-testing(required by vitrageclient)
Add pydot to stein-testing(required by vitrageclient)

Required by vitrageclient in [1].

[1] https://review.rdoproject.org/r/#/c/18039/

Change-Id: I8b7215128ee77ff3b61958501818a2fe621c5081

redhat-openstack/rdoinfo,javierpena/rdoinfo