Self-deadlock in ~Subscription when a callback owns the last reference to another Subscription #1687

~Subscription() calls id2_callback_info.erase() while holding id2_callback_info_mtx, so the erased callback is destroyed with that mutex still held. If that callback holds the last reference to another agnocast::Subscription (e.g. via an agnocast::Client), the inner ~Subscription() locks the same mutex on the same thread and hangs forever. This reproduces on every shutdown of vehicle_door_node in autoware_default_adapi_universe, whose service callback created with relay_service captures a client.