AVRCP: Report no track playing correctly.

If browsing is supported, we cannot use 0x0 (Track selected) as a
generic response per the AVRCP 1.6.1 spec p64.

Rename mTrackNumber => mTracksPlayed to be more accurate, and use media
info to determine if a track is selected instead of whether we've played any.

Test: check with Carkit && PTS: TC_TG_NFY_BV_04_C
Bug: 33414166
Change-Id: I004aa5596ff9aef001ce74c463da0e1ed77b9ff4