Added the ability to configuring the path to an RNG device

Unhardcode settings related to rng devices in nova formula.
The path to an RNG (Random Number Generator) device that will be used
as the source of entropy on the host.

Change-Id: Ifaa71e8bc986143004d0f97298d53b290721f4e8
Related-Prod: PROD-26873 (PROD:26873)
(cherry picked from commit d90200853918667aea4620f38b4d0b71bf2db90a)
8 files changed