Undo preserve_mode=False in order to preserve execute permission

[leekillough]

Fixes #2041

@dhallam @tibdex @tgaddair @mattclay @pselden @jaraco @KOLANICH

[jorikdima]

I suggest not to undo, but make this fix better. I am working on the PR

[jaraco]

Thanks jorikdima. As is revealed by the Appveyor tests, this change causes a test to fail on Windows, a test we put in place to protect the requirement that inspired the change. I would similarly like to see a test to capture the (untested) expectation that this PR is attempting to restore.

[leekillough]

I'm fine with a "correct" fix -- this was just a short-term stop-gap solution.

Let's fix the original issue(s), as well as the regression caused by the lack of execution bits being preserved.