The current implementation allows multiple calls `Close` and `CloseWithError` in every side of the pipe, as a result, the original error can be overwritten.

This CL fixes this behavior adding an error existence check on `atomicError` type
and keeping the first error still available.

Fixes #24283

Change-Id: Iefe8f758aeb775309424365f8177511062514150
GitHub-Last-Rev: b559540d7af3a0dad423816b695525ac2d6bd864
GitHub-Pull-Request: golang/go#33239
Reviewed-on: https://go-review.googlesource.com/c/go/+/187197Reviewed-by: Joe Tsai <thebrokentoaster@gmail.com>
Run-TryBot: Joe Tsai <thebrokentoaster@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>