env: disable aux/timesync in Plan 9 image

TestVariousDeadlines is regularly failing on
the plan9/386 builder running on GCE.

Richard Miller suspects that the failure
may be related to an issue in time measurement,
due to the clock going backward and forward.

A work around would be to disable auth/timesync
to prevent prevent the time from jumping around.

This changes fixes the Plan 9 image by disabling
aux/timesync before starting the buildlet.

Fixes golang/go#26945.

Change-Id: Ibe80cdcd1360cd9e40da70c2c454b6ba2eb44ce9
Reviewed-on: https://go-review.googlesource.com/129098
Reviewed-by: Richard Miller <[email protected]>
Reviewed-by: Brad Fitzpatrick <[email protected]>

Author: 0intro

env/plan9-386/make.bash

@@ -189,6 +189,9 @@ send "echo ramfs -u >>/cfg/helix/cpustart\n"
 expect -exact "term% "
 send "echo aux/randfs -m /dev >>/cfg/helix/cpustart\n"
 
+expect -exact "term% "
+send "echo kill timesync '|' rc >>/cfg/helix/cpustart\n"
+
 expect -exact "term% "
 send "echo >>/cfg/helix/cpustart\n"