Make netd restart when system server hangs on it.

netd has been seen hanging (cause suspected but unconfirmed)
which then brings down the system server which blocks forever
on its main thread trying to connect to netd with its hung
event loop.

This then results in an infinite watchdog runtime restart loop
because the situation never improves:  netd is still borked.

Instead, we should kill netd and give it another chance when
the system server dies.

Bug: 3018996
Bug: 3017876
Change-Id: Ibf9ecf0ffcb78e48c38e5167f21cbeefe0e2a47f

rootdir/init.rc

@@ -323,6 +323,7 @@ service zygote /system/bin/app_process -Xzygote /system/bin --zygote --start-sys
     onrestart write /sys/android_power/request_state wake
     onrestart write /sys/power/state on
     onrestart restart media
+    onrestart restart netd
 
 service media /system/bin/mediaserver
     user media