rng-tools: Fixes for latest OE layouts

The current recipe has a few installation errors:
  * The manipulation of configurable paths drops a '/'
  * The init script defaults are placed in the wrong file
  * Finer control over init script start/stop
  * The default device is non-standard

This patch fixes these little nits and makes the package usable again.

Based on the original patch:
http://patchwork.openembedded.org/patch/41049/



Signed-off-by: Gary Thomas <gary@mlbassoc.com>
Signed-off-by: Ting Liu <ting.liu@freescale.com>
Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>