EnginXCalibrateTest fails on osx 10.9

[quantumsteve]

On the osx 10.9 build, self.zero find a slightly different value of self.zero

Traceback (most recent call last):
File "<string>", line 1, in <module>
File "/Users/svh/Documents/MantidProject/systemtests/StressTestFramework/stresstesting.py", line 347, in returnValidationCode
if self.doValidation():
File "/Users/svh/Documents/MantidProject/systemtests/StressTestFramework/stresstesting.py", line 317, in doValidation
validation = self.validate()
File "/Users/svh/Documents/MantidProject/systemtests/SystemTests/AnalysisTests/EnginXCalibrateTest.py", line 25, in validate
self.assertDelta(self.zero, 3.53, 0.01)
File "/Users/svh/Documents/MantidProject/systemtests/StressTestFramework/stresstesting.py", line 391, in assertDelta
raise Exception(msg)
Exception: Expected 3.51142 == 3.53 within +- 0.01.

[quantumsteve]

This issue was originally trac ticket 11170