Fix error in the role-specific parameter merging in rhsm service
Fix error in the role-specific parameter merging in rhsm service

RhsmVars should be used as the value to be replaced for the global
values, instead of using 'vars'.
Closes-Bug: #1776597

Change-Id: I480b3c51787547b9dd4e1401363a5da7c40798a8

dprince/tripleo-heat-templates,openstack/tripleo-heat-templates,dprince/tripleo-heat-templates,openstack/tripleo-heat-templates