Prepare MOControllerTest for change in PhoneMediaDevice id assignment

Two tests (seemingly unintentionally) rely on the ids assigned by
PhoneMediaDevice being different from the ids assigned by the
system. More details in code.

This is blocking a fix for b/319103067, which is ag/25919934.

I see two options:
- We put in place a fix like the one in this CL.
- We disable these two tests.

In either case, the SysUI owners might want to revisit the decision
later.

Flag: NONE
Bug: b/319103067
Test: atest MediaOutputControllerTest
Change-Id: I05a1f851d8f162152148331bd95ac07112eac730