1128893 - sw-repo-sync does not work for chann that are children of non-custom parent

This pull request is addressing two issues:
        --parent-channel non_custom_parent
        --channel child_channel_of_non_custom_parent
Configuration:
    Base non-custom channel: rhel-x86_64-server-6 
    Child channel of rhel-x86_64-server-6 : epel_repo_6

$ spacewalk-repo-sync   --parent-channel  rhel-x86_64-server-6  --dry-run
|   Channel Label   |   Repository   |
 epel_repo_6 : http:/test.com


 $ spacewalk-repo-sync  --channel epel_repo_6   --dry-run
|   Channel Label   |   Repository   |
 epel_repo_6 : http:/test.com