Override getDeviceId() of mock context

... to return DEVICE_ID_DEFAULT.

AudioManager uses device id of context to dispatch sound effects
asociated with virtual devices to virtual device manager and to
bypass audio focus request for playback on virtual devices with
custom audio policy.

DEVICE_ID_DEFAULT corresponds to default (non-virtual) device.

Bug: 267470284
Test: atest CreateConnectionProcessorTest
AOSP: Context#getDeviceId() is not yet merged in AOSP
Change-Id: I21d15d1077e8a7d45c0b48c673b8e668e263f9fc