Fixes #30649 - self-update for list-versions

[jameerpathan111]

Fixes #30649

Description:
This PR adds support for foreman-maintain upgrade list-versions to check if update for foreman-maintain package is available.

[root@dell-per620-2 foreman_maintain]# ./bin/foreman-maintain upgrade list-versions --help
Usage:
    foreman-maintain upgrade list-versions [OPTIONS]

Options:
    --disable-self-upgrade        Disable automatic self upgrade (default: false)
    -h, --help                    print help

[root@dell-per620-2 foreman_maintain]# ./bin/foreman-maintain upgrade list-versions
Checking for new version of satellite-maintain...

rubygem-foreman_maintain.noarch                                               1:0.6.8-1.el7sat                                                foreman-maintain
Security: kernel-3.10.0-1127.18.2.el7.x86_64 is an installed security update
Security: kernel-3.10.0-1127.el7.x86_64 is the currently running version

Updating satellite-maintain package.

The satellite-maintain package successfully updated.
Re-run satellite-maintain with required options!

[root@dell-per620-2 foreman_maintain]# ./bin/foreman-maintain upgrade list-versions --disable-self-upgrade
6.6.z
6.7

[theforeman-bot]

Issues: #30649

[jameerpathan111]

Ref: PR #305

[jameerpathan111]

@kgaikwad @patilsuraj767 @upadhyeammit need your review.

[patilsuraj767]

LGTM 👍

[kgaikwad]

Thank you @jameerpathan111 👍