Fix cudnn dropout (#15473)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/15473
Revert accidental changes introduced in D13335176
IntList is a range and copying it just copies pointers. Thus pointers would point either on deallocated memory or on the same memory causing equality always pass.
Reviewed By: ezyang
Differential Revision: D13537131
fbshipit-source-id: c97b3533be689bb4cdadd9e612f1284ac50e4bda
