DevSupport - fix small bugs with Host change dialog (#54855)

Summary:
Pull Request resolved: https://github.com/facebook/react-native/pull/54855

I've noticed a couple of bugs with the bundle change dialog:
1. We should not show 2 host change buttons if they're pointing to the same host.
2. The dialog was for some reason writing on `settings.debugServerHost` twice. This has side effects, we should not do it.

Changelog:
[Android] [Fixed] - DevSupport - fix small bugs with Host change dialog

Reviewed By: fabriziocucci

Differential Revision: D88952963

fbshipit-source-id: 3fc6c5c342fff1eac663097e64ca1d44b5b7f5a3