Description of problem:
When running cdn-sync with --no-rpms argument but without --no-packages argument:
1) The packages are not visible in WebUI (while the correct behavior is they are shown but not downloaded/downloadable)
2) The command itself ends "successfully" but with error message (shown for cdn-sync -c rhel-x86_64-server-6 --no-kickstarts --no-errata --no-rpms):
---
08:28:39 failure: Packages/389-ds-base-1.2.11.15-65.el6_7.x86_64.rpm from content_dist_rhel_server_6_6Server_x86_64_os: [Errno 256] No more mirrors to try.
08:28:39 ERROR: failure: Packages/389-ds-base-1.2.11.15-65.el6_7.x86_64.rpm from content_dist_rhel_server_6_6Server_x86_64_os: [Errno 256] No more mirrors to try.
---

How reproducible:
Deterministic

Steps to Reproduce:
1. cdn-sync -c rhel-x86_64-server-6 --no-kickstarts --no-errata --no-rpms
2. View channel packages in WebUI, there are none
3. Notice the command, although ending with "08:28:39 Sync of channel completed in..." and returning 0, shows error mentioned above.

Actual results:
cdn-sync actually fails

Expected results:
No error message, packages in WebUI