revert accidental commit

fairscale/nn/data_parallel/fully_sharded_data_parallel.py

@@ -587,12 +587,14 @@ class FullyShardedDataParallel(nn.Module):
                 assert p.dtype == torch.float32
 
             # If world_size is 1, then we all-reduce grads instead of sharding.
+            p._is_sharded = self.world_size > 1
             p._orig_size = p.data.size()
 
-            if self.world_size == 1:
+            if not p._is_sharded:
                 p._is_sharded = False
                 self.numel_padded_per_param.append(0)
                 continue
+            p._is_sharded = True
 
             # Replace p.data with the relevant shard.
             orig_data = p.data