[Test] Fixed regression in Python 2.6 support

Support for the implcit handling of positional arguments with "{}" isn't
available until Python 2.7.

git-svn-id: https://cantera.googlecode.com/svn/cantera/trunk@2296 02a645c2-efd0-11dd-984d-ab748d24aa7e
[Test/Reactor] Fixed test of sensitivity coefficients

git-svn-id: https://cantera.googlecode.com/svn/cantera/trunk@2297 02a645c2-efd0-11dd-984d-ab748d24aa7e