Revert "Fix vdev_probe() call outside SCL_STATE_ALL lock"

This reverts commit cc9c6bc.

The async zios executed via zio_nowait() are protected by SCL_ZIO which
is taken by the zio pipeline itself in the IO_START stage and released
in the IO_ASSES stage if zio->io_flag does not contain CONFIG_WRITER.

In addition, the vdev_probe() patch causes ztest to fail consistently.

Signed-off-by: Olaf Faaland <faaland1@llnl.gov>

module/zfs/zio.c

@@ -3325,7 +3325,7 @@ zio_vdev_io_done(zio_t *zio)
 
 	ops->vdev_op_io_done(zio);
 
-	if (unexpected_error && zio->io_waiter != NULL)
+	if (unexpected_error)
 		VERIFY(vdev_probe(vd, zio) == NULL);
 
 	return (ZIO_PIPELINE_CONTINUE);