Properly register parameters of LU decomposition

Currently when `lu_decomposed` is set to `True`, loading from a checkpoint doesn't work.

This PR fixes that by properly registering them as a `nn.Parameter` so they will be part of the state dict.

Author: Joost van Amersfoort

glow/modules.py

@@ -208,8 +208,8 @@ def __init__(self, num_channels, LU_decomposed=False):
             l_mask = np.tril(np.ones(w_shape, dtype=np.float32), -1)
             eye = np.eye(*w_shape, dtype=np.float32)
 
-            self.p = torch.Tensor(np_p.astype(np.float32))
-            self.sign_s = torch.Tensor(np_sign_s.astype(np.float32))
+            self.p = nn.Parameter(torch.Tensor(np_p.astype(np.float32)))
+            self.sign_s = nn.Parameter(torch.Tensor(np_sign_s.astype(np.float32)))
             self.l = nn.Parameter(torch.Tensor(np_l.astype(np.float32)))
             self.log_s = nn.Parameter(torch.Tensor(np_log_s.astype(np.float32)))
             self.u = nn.Parameter(torch.Tensor(np_u.astype(np.float32)))