RELAND of Whitelist environment entering recipe engine to match run_slave.
RELAND of Whitelist environment entering recipe engine to match run_slave.

This is mainly for local run_recipe invocations, that we don't accidentally
incorporate environment variables that won't be available on the bots, such
as GYP defines.

Original patch: https://codereview.chromium.org/1252053002/
Revert: https://codereview.chromium.org/1252513003/

BUG=392992,513109
R=iannucci@chromium.org

Review URL: https://codereview.chromium.org/1257433002

git-svn-id: 239fca9b83025a0b6f823aeeca02ba5be3d9fd76@296100 0039d316-1c4b-4281-b951-d872f2087c98

luci/recipes-py,luci/recipes-py,shishkander/recipes-py,shishkander/recipes-py