bigswitch: 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 examples found in bigswitch via a pylint
test.  Other occurrences are addressed elsewhere.

Change-Id: I23fd4e7d0e4173e753a124d62a1563ce6ac674ca
Partial-Bug: #1404788
Tighten dnsmasq version regex

The previous regex forgot to escape the '.', resulting a more liberal
match than intended.  Luckily it continued to work, since the dnsmasq
version is the first number that appears in the --version output.

This change improves the regex to correctly escape the '.' (as
presumably originally intended) and to look for the prefix "version ".

Change-Id: I12548a7b2c21262aa54c84be4e31bda15eab8d52
Merge "Tighten dnsmasq version regex"
Merge "bigswitch: Use lazy logging interpolation"