Only attempt remote logins if directed by the user

Since the system info plugin was defaulting to ohai-solo this
commit moves the check for the user's intention up.

Change-Id: Iccbbd882371131c930f7a951cc88c5628c290464
Closes-Bug: 1295315
Documents OpenStack control plane discovery

Change-Id: I51ddb2477fbaa0215d6621f31d0f7189c8350bac
Merge "Documents OpenStack control plane discovery"