Point to epel-openstack-grizzly.repo in install/deploy guide

(already fixed in basic-install)

Fix bug 1175191

Cherry pick from https://review.openstack.org/#/c/28461/

Change-Id: I1624080df788bc566b965b88fd7130bda391c2fb
Merge "Point to epel-openstack-grizzly.repo in install/deploy guide" into stable/grizzly