define openstack-havana repo as bare link

rdo rpm for some reasons comes with puppetlabs and other useless repos
rpc_backend is set explicitely
tgt conf is differe for rhel/centos
Merge pull request #121 from MirantisDellCrowbar/sbubnov/feature/rhel-havana/hydrogen/master

https://github.com/crowbar/barclamp-cinder/pull/121

Merged by devtool for ArkadyKanevsky