random: entropy tweaks are all the rage nowadays

use nonblocking for all.  Read this web page:
http://lwn.net/Articles/489734/

Change-Id: I91c2a4299593709c0bbb1c6bf5a1096d2469c82c
random: prevent add_input from doing anything

Change-Id: If6cb629788f170d3b904373a7d4ad4829ea69e4b