Remove RHEL6 specific code in prescript.pp
Remove RHEL6 specific code in prescript.pp

Because there are no more EPEL6 repositories on
https://repos.fedorapeople.org/repos/openstack/openstack-juno/
this code can be removed.

Change-Id: I2b212ac1121f27dbc943c86610d14b6bbb52d7b3

mahak/packstack,mahak/packstack,palmer159/openstack-test,mahak/packstack,palmer159/openstack-test,openstack/packstack,stackforge/packstack,stackforge/packstack,palmer159/openstack-test,stackforge/packstack,imcsk8/packstack,openstack/packstack,openstack/packstack,fr34k8/packstack,fr34k8/packstack,xbezdick/packstack,fr34k8/packstack,imcsk8/packstack,xbezdick/packstack,imcsk8/packstack,xbezdick/packstack