SERVER-45491.patch Copied from TIG-2235 to be a SERVER ticket.

When resmoke.py runs replica set tests, the mongod servers log to stdout by default. This can be overridden only by modifying the Javascript test code to pass useLogFiles to ReplSetTest.

It would be useful to me have a way, without modifying the Javascript test code, to make the servers log to files for post-test analysis. I propose a resmoke.py command-line option that enables logging to disk and prevents post-test cleanup of the logfiles.