Remove repeated openstack-config line from yum version

Reported with doc comment:
http://docs.openstack.org/havana/install-guide/install/yum/content/nova-compute.html#comment-1088743139

backport: stable/havana

Change-Id: I8f3036e238456746c3d8323c14e9620610009217
Partial-bug: 1242249
Merge "Remove repeated openstack-config line from yum version"