Merge remotes with the same name

[barthalion]

Speaking about flatpak here, but Alex said that the logic for this is in ostree.

If user has added some remote before, and later a file is dropped to /etc/flatpak/remotes.d/ that adds a remote with the same name, flatpak fails as follows:

error: While opening repository /home/bp/.local/share/flatpak/repo: Multiple specifications found for remote "flathub"

It would be useful if ostree could merge such remotes if their names and url match.

[cgwalters]

Yep see #1166