ensure epel is removed prior to packstack on any distro and doc.

* remove the "when: rhel7" condition
* add doc around why these tasks are present

Change-Id: Ia9ce39a3040ca5d81cf6bd8b215c26dcd3f2c532
fix: install tempest from internal test repo

Change-Id: I6c69394e0f872df4776ca042b39f331167a34480
(cherry picked from commit b9c9051899d9d1161b475c8ee01e529fa59c1408)
Merge remote-tracking branch 'gerrit/master' into dev/reorg

Change-Id: I7dfd7ec0262505a4c90fceadd3262fff24f88d52