A2DP: Don't override the SDP handle if there is processing

The stack could handle only one A2DP find service a time. If there were
2 sinks to reconnect at the same time, the SCB handle for SDP might be
override by the later, but caused this SDP event was routed to worng
handler. And, the earlier would be stuck at opening / closing state to
cause abnormal behavior.
This CL prevents such overridden, and uses Bluetooth address within SDP
results to find its handler.

Bug: 145326274
Test: Reconnect to multiple A2DP sinks
Change-Id: I256859f8c70cc948c03b8ac90bf600bef4fdc3a0