Remap CODE_REJECTED_ELSEWHERE to incoming rejected.

CODE_REMOTE_CALL_DECLINE and CODE_REJECTED_ELSEWHERE are both explicitly
documented as handling the "call rejected elsewhere" multiendpoint usecase.
Yes, they're exactly the same.  And they should be duped in the future.

Fixes: 194079457
Test: To be manually tested by test team (infeasible to development test
locally).

Change-Id: I3e0f33ad2d620bc75b6b723dd3f72277a6fa120f