Setting the logging to debug changes fit parameters in unit tests

[NickDraper]

Setting the root logger level to debug, leads to unit test failures that are related to a call to minimizer->costFunctionVal() in Fit.cpp.

As far as I can follow this should never happen The error show in 2 unit tests, one of which is CurveFittingTest_SeqDomainSpectrumCreatorTest. The error message is

985: In SeqDomainSpectrumCreatorTest::testFit:
985: C:/Mantid/Code/Mantid/Framework/CurveFitting/test/SeqDomainSpectrumCreatorTest.h:277: 
Error: Expected (fun->getParameter(0) == 2.0) up to 1e-6 (0.0000), found (1.9999 != 2.0000)

it can be prevented by removing the following lines in Fit (starting at line 184)

if (g_log.is(Kernel::Logger::Priority::PRIO_INFORMATION)) {
      g_log.debug() << "Iteration " << iter
                    << ", cost function = " << minimizer->costFunctionVal()
                    << "\n";
    }