Switch fileutils to use python logging

oslo.concurrency code needs fileutils from oslo-incubator.
fileutils needs the common copy of log.py. What happens when we
import oslo.concurrency into nova, we end up with duplicate
options for default_log_levels. So to unravel the knots,
we switch fileutils over to python logging and hence remove
the need for common copy of log.py in oslo.concurrency.

Change-Id: Ida7ff3418db7c2a0a5e8b827e1c277533812b8ed
Merge "Switch fileutils to use python logging"