[product: zaphod][project: zaphod-v0.3]: [bug] Remove buggy setUp/tearDown.

SYNOPSIS
[modified]m42/test/test_iputil.py: Rewrote code to not use setUp/tearDown

DETAILS
The technique of assigning a dummy function for testing to iputil
global variables in setUp and tearDown methods poses risks of
generating errors if tests from other test cases are run in between
the setUp and tearDown of iputil_tests. To avoid this, all dummy
function assignment and restoration has been done inside the test
functions themselves. To be safe all restoration is done in a finally
block that ensure execution regardless of outcome.