Handle Disconnect request in AV Opening State handler

Usecase:
1. Uncheck media from settings UI
2. initiate A2dp connection from remote, send AVRCP play from remote

Failure:
A2dp connection stuck in opening state.

Rootcause:
When A2dp is unchecked from settings UI and remote initiated
a2dp connection and AVRCP play, music starts streaming on DUT
since A2dp connection disconnected. As A2dp connection was not
completed, btif state stuck in opening state.

Fix:
Handled the disconnection request in the opening state
so that AV state machine moves to proper state before
processing AVRCP Play.

Test: 1. Uncheck media from settings UI
2. initiate A2dp connection from remote, send AVRCP play

Bug: 35415160
Change-Id: If1cda5b78100419fdc60c97349efafdd4a18d40c
(cherry picked from commit d6e64421)