Add Dropout to blacklist (pytorch#25881)

Summary:
Pull Request resolved: pytorch#25881

Add Dropout to blacklist to avoid the error in eager mode quantization.
ghstack-source-id: 89759536

Test Plan: Test locally in python notebook.

Reviewed By: jianyuh

Differential Revision: D17270826

fbshipit-source-id: bcf43483976740564d7f407838f25c2dbb67b016

torch/quantization/quantize.py

@@ -11,7 +11,7 @@
 import torch.nn.qat as nnqat
 
 
-DEFAULT_SKIP_LIST = [nn.Identity, nn.MaxPool2d, nn.AvgPool2d, nn.AdaptiveAvgPool2d]
+DEFAULT_SKIP_LIST = [nn.Dropout, nn.Identity, nn.MaxPool2d, nn.AvgPool2d, nn.AdaptiveAvgPool2d]
 
 def propagate_qconfig_helper(module, qconfig_dict, skip_list=DEFAULT_SKIP_LIST, qconfig_parent=None, prefix=''):
     r"""This is a helper function for `propagate_qconfig`