Don't overwrite existing __init__.py files in py_binary zips
Don't overwrite existing __init__.py files in py_binary zips

This switches zip from "add" to "update" mode, and only adds
__init__.py where it's not already present.

Fixes: #542

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Change-Id: Id65632d1448b403ad328e4a1619c0d4e8ebfdcb4
Reviewed-on: https://bazel-review.googlesource.com/#/c/2250
MOS_MIGRATED_REVID=106690985

ButterflyNetwork/bazel,Asana/bazel,variac/bazel,spxtr/bazel,kchodorow/bazel-1,perezd/bazel,dinowernli/bazel,variac/bazel,whuwxl/bazel,abergmeier-dsfishlabs/bazel,cushon/bazel,meteorcloudy/bazel,Digas29/bazel,LuminateWireless/bazel,rohitsaboo/bazel,akira-baruah/bazel,damienmg/bazel,kamalmarhubi/bazel,Asana/bazel,juhalindfors/bazel-patches,meteorcloudy/bazel,snnn/bazel,dslomov/bazel-windows,ulfjack/bazel,hhclam/bazel,dslomov/bazel-windows,dinowernli/bazel,snnn/bazel,twitter-forks/bazel,abergmeier-dsfishlabs/bazel,dropbox/bazel,whuwxl/bazel,safarmer/bazel,spxtr/bazel,ButterflyNetwork/bazel,kchodorow/bazel-1,kchodorow/bazel-1,dropbox/bazel,juhalindfors/bazel-patches,Asana/bazel,dinowernli/bazel,mikelalcon/bazel,mikelikespie/bazel,twitter-forks/bazel,katre/bazel,akira-baruah/bazel,kchodorow/bazel,mikelikespie/bazel,aehlig/bazel,werkt/bazel,LuminateWireless/bazel,UrbanCompass/bazel,iamthearm/bazel,werkt/bazel,hhclam/bazel,mrdomino/bazel,mbrukman/bazel,werkt/bazel,zhexuany/bazel,katre/bazel,mikelikespie/bazel,Digas29/bazel,dslomov/bazel,juhalindfors/bazel-patches,snnn/bazel,perezd/bazel,davidzchen/bazel,spxtr/bazel,mrdomino/bazel,mikelikespie/bazel,twitter-forks/bazel,mbrukman/bazel,cushon/bazel,Asana/bazel,mrdomino/bazel,rohitsaboo/bazel,hhclam/bazel,perezd/bazel,dropbox/bazel,juhalindfors/bazel-patches,anupcshan/bazel,dinowernli/bazel,meteorcloudy/bazel,Digas29/bazel,UrbanCompass/bazel,ulfjack/bazel,davidzchen/bazel,dslomov/bazel,whuwxl/bazel,whuwxl/bazel,hermione521/bazel,bazelbuild/bazel,dslomov/bazel,dslomov/bazel,abergmeier-dsfishlabs/bazel,zhexuany/bazel,mikelalcon/bazel,mbrukman/bazel,safarmer/bazel,Asana/bazel,safarmer/bazel,kchodorow/bazel,cushon/bazel,hhclam/bazel,safarmer/bazel,dinowernli/bazel,ulfjack/bazel,hermione521/bazel,whuwxl/bazel,abergmeier-dsfishlabs/bazel,snnn/bazel,anupcshan/bazel,LuminateWireless/bazel,iamthearm/bazel,snnn/bazel,kamalmarhubi/bazel,ulfjack/bazel,snnn/bazel,mrdomino/bazel,aehlig/bazel,rohitsaboo/bazel,dslomov/bazel,damienmg/bazel,bazelbuild/bazel,safarmer/bazel,mikelikespie/bazel,twitter-forks/bazel,mrdomino/bazel,mikelalcon/bazel,juhalindfors/bazel-patches,variac/bazel,UrbanCompass/bazel,kchodorow/bazel,akira-baruah/bazel,aehlig/bazel,damienmg/bazel,damienmg/bazel,zhexuany/bazel,UrbanCompass/bazel,dslomov/bazel-windows,mikelalcon/bazel,abergmeier-dsfishlabs/bazel,zhexuany/bazel,werkt/bazel,kchodorow/bazel-1,dslomov/bazel-windows,zhexuany/bazel,damienmg/bazel,Digas29/bazel,bazelbuild/bazel,dslomov/bazel,davidzchen/bazel,Digas29/bazel,perezd/bazel,aehlig/bazel,katre/bazel,hhclam/bazel,mbrukman/bazel,meteorcloudy/bazel,iamthearm/bazel,UrbanCompass/bazel,katre/bazel,twitter-forks/bazel,werkt/bazel,meteorcloudy/bazel,kamalmarhubi/bazel,snnn/bazel,ButterflyNetwork/bazel,ulfjack/bazel,abergmeier-dsfishlabs/bazel,dslomov/bazel,davidzchen/bazel,bazelbuild/bazel,mbrukman/bazel,aehlig/bazel,damienmg/bazel,iamthearm/bazel,perezd/bazel,spxtr/bazel,aehlig/bazel,davidzchen/bazel,rohitsaboo/bazel,variac/bazel,perezd/bazel,ulfjack/bazel,variac/bazel,dropbox/bazel,bazelbuild/bazel,dinowernli/bazel,cushon/bazel,variac/bazel,zhexuany/bazel,akira-baruah/bazel,meteorcloudy/bazel,twitter-forks/bazel,ButterflyNetwork/bazel,kamalmarhubi/bazel,hhclam/bazel,anupcshan/bazel,kchodorow/bazel-1,katre/bazel,dslomov/bazel-windows,bazelbuild/bazel,meteorcloudy/bazel,davidzchen/bazel,LuminateWireless/bazel,katre/bazel,kamalmarhubi/bazel,kchodorow/bazel-1,akira-baruah/bazel,juhalindfors/bazel-patches,mrdomino/bazel,spxtr/bazel,mikelikespie/bazel,variac/bazel,hermione521/bazel,cushon/bazel,Digas29/bazel,mikelalcon/bazel,kchodorow/bazel,kchodorow/bazel,dropbox/bazel,davidzchen/bazel,mikelalcon/bazel,werkt/bazel,twitter-forks/bazel,rohitsaboo/bazel,whuwxl/bazel,anupcshan/bazel,iamthearm/bazel,ButterflyNetwork/bazel,rohitsaboo/bazel,Asana/bazel,kchodorow/bazel,kchodorow/bazel,LuminateWireless/bazel,iamthearm/bazel,hermione521/bazel,ButterflyNetwork/bazel,spxtr/bazel,aehlig/bazel,kamalmarhubi/bazel,dslomov/bazel-windows,perezd/bazel,damienmg/bazel,safarmer/bazel,cushon/bazel,spxtr/bazel,hermione521/bazel,LuminateWireless/bazel,dropbox/bazel,hermione521/bazel,ulfjack/bazel,akira-baruah/bazel,anupcshan/bazel,UrbanCompass/bazel,mbrukman/bazel,Asana/bazel,juhalindfors/bazel-patches,anupcshan/bazel