block: refresh bs->total_sectors on reopen

After reopening a BlockDriverState, it's possible that the size of the
underlying file has changed.  This for example is covered by test 171.

Right now, this is handled by the raw driver's has_variable_length = true
setting.  Since this will be removed by the next patch, handle it on
reopen instead, together with the existing bdrv_refresh_limits.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-Id: <20230407153303.391121-4-pbonzini@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

block.c

@@ -4918,6 +4918,7 @@ static void bdrv_reopen_commit(BDRVReopenState *reopen_state)
     qdict_del(bs->options, "backing");
 
     bdrv_refresh_limits(bs, NULL, NULL);
+    bdrv_refresh_total_sectors(bs, bs->total_sectors);
 }
 
 /*