Created by: JiayiFeng

1. Create a new channel whose capacity is 2.
2. Send 2 data(0 and 1) into the new channel.
3. Try to send the third data(3) to the channel. For the channel is full, the Send() function will be blocked.
4. Receive() data from the channel with another thread. The first received data should be 0 in my understanding. However, in my test I found it's 3 in fact.

In PR #9387 I did a few modifications in the channel_test to help you replicate the bug:

[ RUN      ] Channel.RecevingOrderEqualToSendingOrderWithBufferedChannel
97: /Users/baidu/Documents/git_workspace/Paddle/paddle/fluid/framework/channel_test.cc:52: Failure
97:       Expected: recv
97:       Which is: 2
97: To be equal to: i
97:       Which is: 0
97: /Users/baidu/Documents/git_workspace/Paddle/paddle/fluid/framework/channel_test.cc:52: Failure
97:       Expected: recv
97:       Which is: 3
97: To be equal to: i
97:       Which is: 1
97: /Users/baidu/Documents/git_workspace/Paddle/paddle/fluid/framework/channel_test.cc:52: Failure
97:       Expected: recv
97:       Which is: 4
97: To be equal to: i
97:       Which is: 2
97: /Users/baidu/Documents/git_workspace/Paddle/paddle/fluid/framework/channel_test.cc:52: Failure
97:       Expected: recv
97:       Which is: 0
97: To be equal to: i
97:       Which is: 3
97: /Users/baidu/Documents/git_workspace/Paddle/paddle/fluid/framework/channel_test.cc:52: Failure
97:       Expected: recv
97:       Which is: 1
97: To be equal to: i
97:       Which is: 4
97: [  FAILED  ] Channel.RecevingOrderEqualToSendingOrderWithBufferedChannel (408 ms)