Set default value of EXTRA_ADD_SELF_MANAGED_CALLS_TO_INCALLSERVICE

true.

Self-managed connections need to bind to special in-call service in
order to expose itself to bluetooth stack.

Bug: 178679937
Test: Manually use duo to make self-managed calls and make sure it's
audible on BT

Change-Id: I7c3c56e9c65d43f598645aee5842e97fd73d300e