Add CTS coverage for Call.Rtt setRttMode and getRttAudioMode

Adds a test to verify that the RTT audio mode can be set and
retrieved correctly using the Call.RttCall APIs.

Flag: EXEMPT test only change
Fixes: 339021435
Test: RttOperationsTest#testSetAndGetRttAudioMode
Change-Id: Iea6bd98e94c9c522bc9a36380d708038067ddf7d
1 file changed