disable module-role-cork by default

module-role-cork's hardcoded corking policy can conflict
with the configurable policy management that is part of
module-router and AudioManager. Since module-router/AM are
enabled by default in demo builds, we must also disable
module-role-cork to avoid conflicting corking policies.

Bug-AGL: SPEC-710

Change-Id: I55442b5c11e711783fb4f890d1f26227c295d122
Signed-off-by: Matt Porter <mporter@konsulko.com>