audio: Add retries for BT proxy port registration

When ModuleBluetooth::createProxy is invoked on BT device
connection, the BT stack may not be fully ready yet,
and port registration can fail. This is an intermittent
state and registration should succeed after retrying.

Bug: 320838889
Test: atest pts-bot:A2DP/SRC/REL/BV-02-I
Change-Id: I0c7cf7c1c6a8ee03ef55b004f89139e3b56ee9cd