Prevent test-log.cc from creating log files.

R=dcarney@chromium.org
TEST=cctest/test-log/EquivalenceOfLoggingAndTraversal

Review URL: https://codereview.chromium.org/23526073

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@16852 ce2b1a6d-e550-0410-aec6-3dcde31c8c00