Escape newlines when writing enviroment values to execution logs.
Escape newlines when writing enviroment values to execution logs.

On gLinux platform, {bundle,properties,proto,run}_test.py fail due to
hitting an assertion when writing out a step environment variable value
that contains newlines.

Change-Id: I133e26d71ac7699a4251866b0fe0fa9200868b3f
Recipe-Nontrivial-Roll: skia
Reviewed-on: https://chromium-review.googlesource.com/c/infra/luci/recipes-py/+/1620665
Commit-Queue: Robbie Iannucci <40f3d43a28ebae3cb819288542e1c84d73d962d5@chromium.org>
Auto-Submit: Garrett Beaty <a0767768af30bcbe01b6de5024355c539362a830@chromium.org>
Reviewed-by: Robbie Iannucci <40f3d43a28ebae3cb819288542e1c84d73d962d5@chromium.org>

luci/recipes-py,luci/recipes-py