env/freebsd-amd64: don't restart buildlet on exit

"Graceful termination" of the bot results in the swarming bot process
exiting with code 0. It should not start again after graceful shutdown
(GCE provider will eventually delete the VM).

Drop the restart flag so that daemon won't automatically restart the
service.

Updates golang/go#72030.

Change-Id: I6a6a636c74e3d2b14d9b596eaa4a3d17b89a3de0
Reviewed-on: https://go-review.googlesource.com/c/build/+/741224
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Dmitri Shuralyov <dmitshur@golang.org>

env/freebsd-amd64/buildlet

diff --git a/env/freebsd-amd64/buildlet b/env/freebsd-amd64/buildlet
index 6351302..aedd424 100755
--- a/env/freebsd-amd64/buildlet
+++ b/env/freebsd-amd64/buildlet
@@ -12,7 +12,7 @@
 pidfile="/var/run/${name}.pid"
 suppidfile="/var/run/${name}-sup.pid"
 command=/usr/sbin/daemon
-command_args="-r -fc -p ${pidfile} -P ${suppidfile}"
+command_args="-fc -p ${pidfile} -P ${suppidfile}"
 command_args="${command_args} ${procname}"
 start_precmd="${name}_prestart"
 stop_cmd=":"