[WIP] Skip UNIX-specific tests so they don't break Windows builds.

This PR is meant for discussion rather than merging straight away.

Some of the existing tests are clearly UNIX specific. I have created a new test group for them and excluded it explicitly from the tests.
Should I
  * move the tests to the Integration group
  * Find a way to decide at runtime whether the test should be executed based on the current platform
  * or make them pass on windows as well
With use of RecordingSshTool, we shouldn't be executing any of these commands I thought; where does it fail?
If brooklyn sees that the target location is an ssh'able machine (rather than Windows) then presumably these commands will match whether executed from windows or linux?
If the problem is that we're using localhost, then can we change setUp to pass in an ssh'able machine location instead?