default-distrovars: Add DISTRO_FEATURES_INITMAN to DISTRO_FEATURES

default-distrovars: Add DISTRO_FEATURES_INITMAN to DISTRO_FEATURES

This is a more generic way to set the init manager since we
plan to support other init managers as well.
I will use this variable as a switch to turn on/off any
init scheme that we might support in the future.
By default we use sysvinit.

(From OE-Core rev: 87f06346728bda000c0c0f95312b6a0a1b149ab4)

Signed-off-by: Radu Moisan <radu.moisan@intel.com>
Signed-off-by: Ross Burton <ross.burton@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>