dc323b1351
Server.clientsAtomic was introduced in 6b729795c3 as a lock-free
mirror of Server.clients to skip Server.mu on the packet send hot
path. This drops the non-concurrent map and makes all the existing
callers of the old plain map just use the concurrent map, but still
holding Server.mu.
BenchmarkLookupDestHashTrie is unchanged at ~2ns/op.
Fixes #19726
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>
Change-Id: I0894e4d86914d152b9b5fef969a3184bcb96f678