block: Don't wait for requests in bdrv_drain*_end()

The device is drained, so there is no point in waiting for requests at
the end of the drained section. Remove the bdrv_drain_recurse() calls
there.

The bdrv_drain_recurse() calls were introduced in commit 481cad48
in order to call the .bdrv_co_drain_end() driver callback. This is now
done by a separate bdrv_drain_invoke() call.
Signed-off-by: NKevin Wolf <kwolf@redhat.com>
Reviewed-by: NPaolo Bonzini <pbonzini@redhat.com>
Reviewed-by: NStefan Hajnoczi <stefanha@redhat.com>

block/io.c

@@ -299,7 +299,6 @@ void bdrv_drained_end(BlockDriverState *bs)
 
     bdrv_parent_drained_end(bs);
     bdrv_drain_invoke(bs, false);
-    bdrv_drain_recurse(bs);
     aio_enable_external(bdrv_get_aio_context(bs));
 }
 
@@ -400,7 +399,6 @@ void bdrv_drain_all_end(void)
         aio_enable_external(aio_context);
         bdrv_parent_drained_end(bs);
         bdrv_drain_invoke(bs, false);
-        bdrv_drain_recurse(bs);
         aio_context_release(aio_context);
     }