net/colo-compare.c: Create event_bh with the right AioContext

net/colo-compare.c: Create event_bh with the right AioContext

qemu_bh_new will set the bh to be executed in the main
loop. This causes crashes as colo_compare_handle_event assumes
that it has exclusive access the queues, which are also
concurrently accessed in the iothread.

Create the bh with the AioContext of the iothread to fulfill
these assumptions and fix the crashes. This is safe, because
the bh already takes the appropriate locks.

Signed-off-by: Lukas Straub <lukasstraub2@web.de>
Reviewed-by: Zhang Chen <chen.zhang@intel.com>
Reviewed-by: Derek Su <dereksu@qnap.com>
Tested-by: Derek Su <dereksu@qnap.com>
Signed-off-by: Zhang Chen <chen.zhang@intel.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>