Remove pushMerge from keystoneclient refs/for/refs acl

As discussed in IRC (in #openstack-infra) the pushMerge for the
refs/for/refs/* location shouldn't be required and is being removed
from the ACL.

Change-Id: I88a1fc26fa82c7ca04868dac03956579824f15c1
Merge "Remove pushMerge from keystoneclient refs/for/refs acl"