Description of problem:
The ansible installer supports setups with components such as etcd on separate hosts. etcd is installed from the "rhel-7-server-extras-rpms" channel, however the installer will still enable "rhel-7-server-ose-3.1-rpms" which consumes an OpenShift entitlement but is not actually used to install any software.

The installer should be smart enough to enable only the channels that are needed and not enable "rhel-7-server-ose-3.1-rpms" on nodes that will not install any software from it.

Version-Release number of selected component (if applicable):
3.1

How reproducible:
Always

Steps to Reproduce:
1. install node to be a etcd hosts
2. enable base and extras channel on it
3. configure it as etcd in /etc/ansible/hosts
4. start install process

Actual results:
two options:
1) OSE channel available - it's attached
2) OSE channel unavaiable - setup fails even though all software present

Expected results:
Install completes and finishes successfully. No extra channels are added.