HCI Classic ACL: Queue pending connection requests

* Send next connection request after connection_complete event, if there
is already a pending outgoing connection_request,
accept_connection_request, or reject_connection_request.
* Don't allow sending connection_request, or accept connection, if there
is already a device with same Address connected.
* Also fix a memory leak in grpc_root_server and inquiry_test.

Bug: 143620554
Test: bluetooth_test_gd and cert/run_cert.sh
Change-Id: I4ea321eafa7857bfa3ad3fdfa0ebfa07a162ff4b