Description of problem:
When deleting repos associated to RHUI, the synced content stays on the disk. A user has to delete it manually via pulp-admin for example. Adding 'rm - remove orphan content' into rhui-manager could be a good feature.

Version-Release number of selected component (if applicable):
iso 20161122

How reproducible:
always

Steps to Reproduce:
1. add some repos
2. sync them
3. delete them
4. check disk space or /var/lib/rhui/remote_share
5. check orphans via pulp-admin

Actual results:
pulp-admin -u admin -p admin orphan list
+----------------------------------------------------------------------+
                                Summary
+----------------------------------------------------------------------+

Distribution:            0
Docker Blob:             6
Docker Image:            0
Docker Manifest:         8
Docker Tag:              8
Drpm:                    0
Erratum:                 5336
Iso:                     0
Ostree:                  1
Package Category:        29
Package Environment:     6
Package Group:           476
Rpm:                     39775
Srpm:                    2131
Yum Repo Metadata File:  3
Total:                   47779