[cherry-pick] Fix async update

[cherry-pick] fix pserver optimize blocks

Merge pull request #11728 from typhoonzero/fix_paraexe_bcast

Fix dist train broadcasting bug

[cherry-pick] fix sparse update in parallelExecutor

fix pserver sub-blocks

fix sparse paraexe dist train

Fix async update failed

Update api.rst (merge to release/0.14.0)

Fix kill fail bug (#11635)

* 1. Remove PYTHON_FLAGS from paddle_build.sh in paddlepaddle/paddle:latest-dev

* 1. Add PYTHON_FLAGS back
2. Change SIGKILL to SIGINT and SIGTERM

* 1. Add setup.py.in back

* 1. add pip install open-cv in Dockerfile to avoid libusb_exit hanging up which is caused by the opencv-python package missing

* 1. Add the && \ to line above

* 1. Remove the notice comment

cherry-pick: fix indentation error

* Fix Parallel Exe(VarHandel's version)

* Fix broadcast

* enhance ParallelExecutor stable

Merge pull request #11622 from panyx0718/doc

disable the LODTensor warning for now

Cherry Pick the documentation PRs.

* "add some api reference"

* "fix based on preview"

* "fix evaluator"

* "remove template doc"

* "add doc for exec"

* "add more changes"

* "fix based on preview"

* "chagne code format"

Merge pull request #11608 from panyx0718/doc

small thread-safety fix and doc improvements.

move dist codes from  operaotrs/detail to operators/distributed

overlap rpc op memcpy in distributed training

Fix concat compile warning

Add bilinear interp supporting for uint8

Polish Non-Layer API

add url of cuda9.0_cudnn7_avx_mkl library

fix auc