bridge: Inline iterate_and_prune_ifaces() and remove it.

bridge: Inline iterate_and_prune_ifaces() and remove it.

The main reason that iterate_and_prune_ifaces() existed was because it was
somewhat inconvenient to iterate across all of the interfaces, especially
if anything needed to be deleted.  Now that we've switched from arrays to
lists and hmaps, it's a bit easier, and certainly it's easier to read code
when there aren't any callbacks involved, so inline what this was doing.

This was the only remaining caller of iterate_and_prune_ifaces() so this
removes that function as well as the callback.