watchdog: prioritize stopping it over all else during reboot

A device hanging itself up during shutdown as part of a reboot is stupid.
Therefore, the first to do when initiating a reboot is to stop the watchdog.

The processes stopped before the watchdog where:
K15svscanboot.sh -> ../init.d/svscanboot.sh
K20dbus-1 -> ../init.d/dbus-1
K20dnsmasq -> ../init.d/dnsmasq
K20hwclock.sh -> ../init.d/hwclock.sh
K20resolv-watch -> ../init.d/resolv-watch
K20syslog -> ../init.d/syslog
K20watchdog -> ../init.d/watchdog

With this commit its the first thing.

Wouldn't this risk interrupting a reboot that was otherwise OK?

No the kernel driver expects a write to the watchdog device every minute.
The userland watchdog process updates the kernel every 10 seconds: stopping
it therefore leaves at least 50 seconds for the device to reboot.

Also add a message to the syslog, to make the log file clear:
Aug 17 11:07:07 ccgx user.notice shutdown[2127]: shutting down for system reboot
Aug 17 11:07:07 ccgx daemon.info init: Switching to runlevel: 6
Aug 17 11:07:07 ccgx user.notice root: Stopping watchdog (keeping hw watchdog alive)
Aug 17 11:07:07 ccgx user.crit kernel: [  236.577026] omap_wdt: Unexpected close, not stopping!

closes victronenergy/venus#312

meta-venus/recipes-extended/watchdog/files/init

@@ -38,6 +38,7 @@ case "$1" in
   stop)
 	# note: this forcefully kill the watchdog process, keeping the hw watchdog active
 	echo "Stopping $DESC (keeping hw watchdog alive)"
+	logger "Stopping $DESC (keeping hw watchdog alive)"
 	killall -9 watchdog
 	;;
   disable)

meta-venus/recipes-extended/watchdog/watchdog_%.bbappend

@@ -11,7 +11,7 @@ SRC_URI += "\
 
 INITSCRIPT_PACKAGES = "${PN}"
 INITSCRIPT_NAME_${PN} = "watchdog"
-INITSCRIPT_PARAMS_${PN} = "start 80 S . stop 20 0 1 6 ."
+INITSCRIPT_PARAMS_${PN} = "start 80 S . stop 00 0 1 6 ."
 
 do_compile_append () {
 	${CC} ${CFLAGS} ${LDFLAGS} -DMACH_${MACHINE} \