Fixes #24422 - k-c-h Check hostname is not current hostname

[johnpmitsch]

For katello-change-hostname, often times users will use
hostnamectl to change the hostname before running k-c-h.
This causes the script to error out and leaves things in
a bad state. This commit adds a check that the hostname
specified is different than the current system's hostname.

For plugin updates, please indicate which repos this should be built into:

• Nightly
• 1.19
• 1.18
• 1.17

See Foreman's plugin maintainer documentation for more information.

---

[ekohl]

This will need a release bump as well

[johnpmitsch]

@ekohl updated, let me know if I bumped the release incorrectly with the new formatting

[johnpmitsch]

To review:

• Spin up a "newish" katello production installation (I would say 3.7+, nightly would be best).
• clone foreman-packaging and checkout this PR
• snapshots are highly encouraged at this point since you are dealing with katello-change-hostname, which heavily modifies a system. 😉
• run ./packages/katello/katello/katello-change-hostname -u admin -p changeme $(hostname -f), this should fail with a warning since its trying to change the hostname to current hostname of the box.
• run ./packages/katello/katello/katello-change-hostname -u admin -p changeme <NEW_HOSTNAME> using a new hostname in place of <NEW_HOSTNAME> and ensure the script completes successfully.
• check anything else you deem important, such as changing the hostname first with hostnamectl and trying to use katello-change-hostname to change to that hostname (this is the behavior we are trying to prevent).