Use xargs -0 instead of --null

This gives compatibility with OS X in the test.

Change-Id: Ic7ec31f8d8ab40654c81992b3fc2b8f1f1b73b4c
install-guide: no need to reboot twice

Commit 2a8fee9 didn't remove an unnecessary 'reboot' call.

Change-Id: Ie4700bf638b245b3b6a55a6d0e3def887921f97c
Merge "Use xargs -0 instead of --null"
Merge "install-guide: no need to reboot twice"