Fix push script for autoroll account.

Push tags to the repo not to the remote - which is a cache
checkout on the bots.

Add new files when doing pure svn commits. Otherwise, new
files are silently ignored and not committed.

BUG=408523
LOG=n
TEST=script_test.py
TBR=tandrii@chromium.org

Review URL: https://codereview.chromium.org/699493004

Cr-Commit-Position: refs/heads/master@{#25049}
git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@25049 ce2b1a6d-e550-0410-aec6-3dcde31c8c00