exclude libbitcoinconsensus-0.dll tests when not on windows (#1489)
exclude libbitcoinconsensus-0.dll tests when not on windows (#1489)

Check if the tests are running on Windows before executing them.
This will fix the NBitcoin tests relying on libbitcoinconsensus-0.dll.

![image](https://user-images.githubusercontent.com/1867877/41133042-96e4088e-6abc-11e8-8fb4-fb5bc24ed52e.png)

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