[Chromedriver] Retry deleting temp dir when needed

Occasionally ChromeDriver may fail to delete temporary directories
while exiting, causing wasted disk space. This change adds retry
logic while cleaning up these directories.

BUG=chromedriver:644

Review-Url: https://codereview.chromium.org/2853953002
Cr-Commit-Position: refs/heads/master@{#469199}
5 files changed