Fixes 6041: Convert katello-debug to be an extension of foreman-debug

Forman debug now allows plugins to add there own debug extensions.
This patch converts the katello debug into such an extension. It also
adds the etc/pulp/server/plugins.conf.d/nodes/distributor directory
to the list of files which are collected. Finally, the spec file is updated
for packaging.
Merge pull request #4207 from bkearney/katello-debug

Fixes 6041: Convert katello-debug to be an extension of foreman-debug