Suppress error handling for test coverage in push and merge scripts.

- This adds a suppression of lines concerning error handling for the test coverage analysis
- Fixes also calling push-to-trunk from auto-roll

TEST=tools/push-to-trunk/script_test.py
TBR=ulan@chromium.org

Review URL: https://codereview.chromium.org/196883003

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@19838 ce2b1a6d-e550-0410-aec6-3dcde31c8c00