qtest: add qtest_add_abrt_handler()

Allow a test to add abort handlers, use GHook for all handlers.

There is currently no way to remove a handler, but it could be
later added if needed.

Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Reviewed-by: Claudio Fontana <claudio.fontana@huawei.com>