* don't try to re-Start (and thus create a new client) during Shutdown
* in tests, wait for controlclient to fully shut down when replacing it
* log a bit more
Updates tailscale/corp#14139
Updates tailscale/corp#13175 etc
Updates #9178 and its flakes.
Change-Id: I3ed2440644dc157aa6e616fe36fbd29a6056846c
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>