Description of problem:
Spacewalk-remove-channel tool voids to remove

Version-Release number of selected component (if applicable):
spacewalk-backend-tools-1.2.13-52.el6sat.noarch

How reproducible:
deterministic

Steps to Reproduce:
1. Create channel with 2 dummy packages
2. Create an erratum, including the newer package
3. Remove the erratum
4. spacewalk-remove-channel -v -u -c ${channel}
  
Actual results:
The output of spacewalk-remove-channel looks sane, but the packages
previously included in the erratum are not deleted.

Expected results:
All packages deleted, as they are not needed.
(neither by another channel nor by an existing erratum)

Additional info:
None