Prozlach/unittests

Unittests for check-zonesync
You are mostly right - I have fixed it where it made sense. Sometimes it is unavoidable though:
* when I just want to make sure that a method was not called:
```
self.assertFalse(ScriptStatusMock.notify_immediate.called)
```
* I think that I should not be testing error messages, only the severity of the message and let the body change at will. The assert_* methods allow me to only check whole call. So sometimes I resort to this:
```
self.assertEqual(ScriptStatusMock.notify_immediate.call_args[0][0],'unknown')
```