Fixing python 2.6 errors
Fixing python 2.6 errors

Issues: Issue #167

Problem: Build uncovered errors when running iapp_parser unit test in
python 2.6

Analysis: Change string.format to use variable replacement with
percentage sign.

Tests: All tests passing

F5Networks/f5-common-python,wojtek0806/f5-common-python,F5Networks/f5-common-python