Add mistral-lib package
Add mistral-lib package

mistral-lib is a new dependency for Mistral. It provides an interface
for writing custom actions. It is added to Mistral in review:
https://review.openstack.org/453517

Package review is in https://bugzilla.redhat.com/show_bug.cgi?id=1441221

The under-review tag has been added until the initial import has been
completed.

Change-Id: I7ec8ada798110b7ce1dbebd337e1da5ab8ad2639

javierpena/rdoinfo,redhat-openstack/rdoinfo