Revert "[step_runner] Specify close_fds to avoid leaking non-std handles to steps."
Revert "[step_runner] Specify close_fds to avoid leaking non-std handles to steps."

This reverts commit e5b95408b9e4b89a7b88f67c40b3af79a88a7ad7.

Reason for revert: broke Win builders in **many** places.

Original change's description:
> [step_runner] Specify close_fds to avoid leaking non-std handles to steps.
> 
> R=​jchinlee@chromium.org, martiniss@chromium.org, a30c74fa30536fe7ea81ed6dec202e35e149e1fd@chromium.org
> 
> Bug: 929965
> Change-Id: I5aaeaadfc0578565591e50828c9b2bc9d0dde701
> Reviewed-on: https://chromium-review.googlesource.com/c/1460319
> Reviewed-by: Jao-ke Chin-Lee <jchinlee@chromium.org>
> Commit-Queue: Robbie Iannucci <iannucci@chromium.org>

TBR=iannucci@chromium.org,jchinlee@chromium.org,a30c74fa30536fe7ea81ed6dec202e35e149e1fd@chromium.org,martiniss@chromium.org

Change-Id: I19d042669b6b17104197b0bf7f269ca048bf34cd
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: 929965, 930038
Reviewed-on: https://chromium-review.googlesource.com/c/1460568
Reviewed-by: Andrii Shyshkalov <a30c74fa30536fe7ea81ed6dec202e35e149e1fd@chromium.org>
Commit-Queue: Andrii Shyshkalov <a30c74fa30536fe7ea81ed6dec202e35e149e1fd@chromium.org>

luci/recipes-py,luci/recipes-py