Bluetooth A2DP Sink only connect from Disconnected state

While in the pending or Connected state ignore CONNECT calls since
the A2DP sink is already in the process of connecting or
disconnecting to a target device.

Bug: 76096462
Test: While connected to a device attempt to change connection to
another device.

Change-Id: I533bf526ccb1d65b3eebf3b04ea95882ce0cdb74