set stream for cudnn handle correctly in cudnn wapper
set stream for cudnn handle correctly in cudnn wapper

Summary:
CuDNNWRapper inline_cudnn_handle() should set the stream every time, since it can change. This caused problems in RNN scenarious. Also this bug rendered singlethread_async_net incorrect / slow!

I found out the problem by using nvprof --print-gpu-trace and noticing that some kernels were run in different stream than i expected.

Reviewed By: ajtulloch, Yangqing

Differential Revision: D5758426

fbshipit-source-id: 651c62fe28eaf09e1675d4adf3f1fac8b4c8e75b

Yangqing/caffe2,pietern/caffe2,davinwang/caffe2,Yangqing/caffe2,xzturn/caffe2,Yangqing/caffe2,davinwang/caffe2,Yangqing/caffe2,xzturn/caffe2,pietern/caffe2,pietern/caffe2,xzturn/caffe2,sf-wind/caffe2,sf-wind/caffe2,sf-wind/caffe2,xzturn/caffe2,sf-wind/caffe2,davinwang/caffe2,xzturn/caffe2,davinwang/caffe2,pietern/caffe2,caffe2/caffe2,davinwang/caffe2,pietern/caffe2,sf-wind/caffe2,Yangqing/caffe2