Description of problem:
When running "yum clean plugins" or "yum clean all", the product-id metadata files are not removed from the yum cache.

I'm not sure if this is by design or just hasn't been considered yet.  However, I think the product-id plugin should define the clean hook and remove the files it fetches.

Reason I'm filing this:

Starting with RHEL-7.6, after "yum clean all" does its usual thing, it recurses into the cachedir and looks for any uncleaned data.  If some is found, the message "Other repos take up ... of disk space" is printed, to inform the user of the fact that manual clean-up might be necessary.

The message has been added because people would incorrectly think that "yum clean all" would really purge everything.  Whereas in reality, it only affects the enabled repos and the current releasever/arch combination (so-called "operational cachedir").  Had they ever disabled or removed a repo or fetched some repos with a different --releasever, they would have been surprised why a "yum clean all" still leaves files behind in the cachedir.

Now, since the productid files are never removed (not even from the operational cachedir), yum would always detect these and show the "Other repos take up..." message.  That defeats the purpose of the hint as it's basically a false positive.

In case there's an actual reason for keeping those productid files around even after a clean-up, I guess yum could specifically ignore these in the detection routine.  If you think so, please reassing this BZ to yum.

Version-Release number of selected component (if applicable):
yum-3.4.3-161.el7.noarch

How reproducible:
100%

Steps to Reproduce:
1. Subscribe your system to CDN
2. Make sure the default CDN repos are enabled
3. # yum makecache
4. # yum clean all

Actual results:

Loaded plugins: product-id, search-disabled-repos, subscription-manager
Cleaning repos: rhel-7-server-rpms
Other repos take up 3.7 k of disk space (use --verbose for details)

Expected results:

Loaded plugins: product-id, search-disabled-repos, subscription-manager
Cleaning repos: rhel-7-server-rpms

Additional information:

# yum clean all --verbose
[...]
Cleaning repos: rhel-7-server-rpms
Operating on /var/cache/yum/x86_64/7Server (see CLEAN OPTIONS in yum(8) for details)
Disk usage of /var/cache/yum/*/* after cleanup:
2.1 k  enabled repos:
  2.1 k  /var/cache/yum/x86_64/7Server/rhel-7-server-rpms
0      disabled repos
0      untracked repos
37     other data:
  37     /var/cache/yum/x86_64/7Server/timedhosts
2.1 k  total

# ls -l /var/cache/yum/x86_64/7Server/rhel-7-server-rpms
total 4
drwxr-xr-x. 2 root root    6 Nov  1 10:17 gen
drwxr-xr-x. 2 root root    6 Nov  1 10:16 packages
-rw-r--r--. 1 root root 2159 Oct 29 23:31 productid