Ignore minor precision differences in test.

The test which uses ProducerWithPSetDesc was failing under gcc490
because python and C++ disagreed on the value of double(0.3) on the
last bit in the precision. The test was changed to accept a tolerance
of 1E-6.
Merge pull request #2485 from Dr15Jones/avoidPrecisionProblemInTest

Misc fixes -- Ignore minor precision differences in test.