Ensure MediaRouter correctly handles renamed Wifi displays.

Fix a couple of bugs that cause MediaRouter to disconnect from
the current Wifi display whenever it is renamed.

Added an extra check in WifiDisplayAdapter for identity renames.
The Settings app already handles this case but it's good to have
the service check for it as well so we don't store unnecessary
aliases.

Bug: 7310777
Change-Id: I8fddd32ca59f9b798ee31b467b81457508c345f8