Add pkg.list_repo_args to yumpkg5

This commit adds a new function to yumpkg5 which allows you list the
packages available in the different repositories. This can be used to
get the repo name and version number to aid in configuring version
pinning in states.

This also changes list_pkgs to use repoquery, since rpm does not support
the REPOID tag in a queryformat string.
Merge pull request #9253 from terminalmage/list-repo-pkgs

Add pkg.list_repo_args to yumpkg5