Use lazy logging interpolation

There are a small number of examples of "eager" interpolation in
neutron:
  logging.debug("foo %s" % arg)

These should be converted to perform the interpolation lazily within
the logging function, since if the severity is below the logging level
then the interpolation can be skipped entirely.

This change addresses all such current examples found in neutron core
via a pylint test.  Vendor plugins and services are fixed elsewhere.

Change-Id: I823d8453cd76e4985cabd31ca6b939f43a80b36c
Partial-Bug: #1404788
Merge "Use lazy logging interpolation"