MockAclConnection: Use a real queue for testing

Instead of letting user specify an ACL queue during mock, let
MockAclConnection provide a queue. This allows testing upper layer
without mocking all the way down to ACL connection layer.

Test: bluetooth_test_gd
Bug: 144375926
Change-Id: I9ae6ff2c7ab124f8e6b05c6152a263db7b5c16ff