using push options for presubmit/autosubmit votes affects every patch in a multi-commit upload

[DanAlbert]

Uploading with --autosubmit or --presubmit causes those votes to be applied to every patch in the stack for a multi-commit upload. This is how gerrit interprets the push options, so we can't trivially fix this.

We should probably stop using the push options and instead make a gerrit API call after upload to ensure that the votes are only set on the top-most patch.