9538e9f97035ce7a382d2b395db3368bd0326113 broke LocalBackend.WhoIs
where you can no longer lookup yourself in WhoIs.
This occurs because the LocalBackend.peers map only contains peers.
If we fail to lookup a peer, double-check whether it is ourself.
Fixes#9470
Signed-off-by: Joe Tsai <joetsai@digital-static.net>
Co-authored-by: Rhea Ghosh <rhea@tailscale.com>