Add last-push check to automatic push-to-trunk script.

Make sure the script is not trying a push-to-trunk twice in a row.

This also passes through some command line parameters.

TEST=python -m unittest test_scripts.ScriptTest.testCheckLastPushRecently
R=ulan@chromium.org

Review URL: https://codereview.chromium.org/103533003

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@18306 ce2b1a6d-e550-0410-aec6-3dcde31c8c00