Resume prelu_op_test in python2

* fix dist train reduce mode

* fix previous fix

* fix dist transpile with memopt

* update api.spec

* polish dist transpile api

* update apispec

* update apispec

* refine dist train RPC deps

* clean up

* clean up

* fix ut

* remove input for fetch_barrier

* follow comments

* dist transpiler add control dependency var between send and recv

* fix async deps

* follow comments and refine

* fix deps connect for rpc ops

* Fuse Convolution and Eltwise Add into Conv+Bias

* Reduce bias branching at conv_mkldnn_op

* Add MKLDNN build checks for Conv Bias

* Conv-bias: check if bias input exist befor assignment

* Conv-bias: Remove Bias dim check from infershape

It was causing conv3d test to crash upon\ncalling HasInput(Bias)

* add async dist tests

* update delta

* fix transformer test

* refine rmsprop transpile

* update

* fix dist seresnet

Port dist_transpiler new added codes
Port ut for clone desc

Add dependency to send recv

* dist transpile can pass startup program by argument

* update API.spec

* hide misc APIs

* update

* fix transformer test

* update API.spec

* fix dist train with rmsprop

* add rmsprop transpiler test

* update by comment

Fix pb_protobuf2 FromString problem