Description of problem:
When running spacewalk-channel -a -c <PARENT CHANNEL> on a system with no channel subscriptions, it's not possible to add a parent/base channel. The error below is shown.

This is because there's a check to ensure the channel being added is a child of the system's parent channel, but the check takes place even if you're supplying a parent channel and if the system is not subscribed to any channels.

Error message: 

Error communicating with server. The message was:

Error Message:
    Parent of channel <PARENT CHANNEL> is not subscribed to server
Error Class Code: 32
Error Class Info: Channel error

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

How reproducible:
spacewalk-channel -a -c <PARENT CHANNEL> on a system with no channel subscriptions

Actual results:
Error as above. System not subscribed.

Expected results:
System should be subscribed.