Add audio management between Media Player and Radio.

This patch enables loading router-module by default to manage audio routing
when both Media Player and Radio start playing.
Latter audio source selected by user enforces existing one corked.

Detail in below.
https://jira.automotivelinux.org/browse/SPEC-378

Bug-AGL: SPEC-606

Change-Id: I407924b1346f95573596434ba9b17c732cae5146
Signed-off-by: Toshiaki Isogai <isogai.toshiaki@nttd-mse.com>
Signed-off-by: Scott Murray <scott.murray@konsulko.com>