Use thread_pool_submit_co, instead of reinventing it here. Note, that
thread_pool_submit_aio() never returns NULL, so checking it was an
extra thing.
Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: Alberto Garcia <berto@igalia.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Message-id: 20190506142741.41731-4-vsementsov@virtuozzo.com
Signed-off-by: Max Reitz <mreitz@redhat.com>