This doesn't cause any practical problems as it is,
but vet (rightly) flags this code as copying a mutex.
It is easy to fix, so do so.
Signed-off-by: Josh Bleecher Snyder <josh@tailscale.com>
Adds a test that will fail consistently on 32-bit platforms if the
struct ever changes again to violate the rules. This is likely not
needed because unaligned access crashes reliably, but this will reliably
fail even if tests accidentally pass due to lucky alignment.
Signed-Off-By: David Anderson <danderson@tailscale.com>