Dont run StopwatchDisposable_MeasuresPerformanceCorrectly test in Mac OSX (#813)
Dont run StopwatchDisposable_MeasuresPerformanceCorrectly test in Mac OSX (#813)

* Dont run this test in a mac osx environment

* Review fix as per Aprogiena's review

Aprogiena/StratisBitcoinFullNode,bokobza/StratisBitcoinFullNode,mikedennis/StratisBitcoinFullNode,bokobza/StratisBitcoinFullNode,mikedennis/StratisBitcoinFullNode,Neurosploit/StratisBitcoinFullNode,stratisproject/StratisBitcoinFullNode,stratisproject/StratisBitcoinFullNode,mikedennis/StratisBitcoinFullNode,fassadlr/StratisBitcoinFullNode,Aprogiena/StratisBitcoinFullNode,Neurosploit/StratisBitcoinFullNode,Neurosploit/StratisBitcoinFullNode,mikedennis/StratisBitcoinFullNode,Aprogiena/StratisBitcoinFullNode,quantumagi/StratisBitcoinFullNode,bokobza/StratisBitcoinFullNode,bokobza/StratisBitcoinFullNode,quantumagi/StratisBitcoinFullNode,fassadlr/StratisBitcoinFullNode