Add python-sphinxcontrib-programoutput to stein build deps
Add python-sphinxcontrib-programoutput to stein build deps

This package was already included up to queens, and now it is a new
build dependency for manilaclient, see [1].

[1] - https://review.openstack.org/#/c/595362/6/doc/requirements.txt

Change-Id: I795aae15105ae1e496f27fb1f89c92411e02ae65

javierpena/rdoinfo,redhat-openstack/rdoinfo