Fix #590: Systeminfo doesn't resolve Windows correctly (#592)

This PR is to fix issue #590. It includes the platform module to resolve
the OS type correctly. This enables tests running againt `WinRM` to
behave correctly if a MSYS2 is installed on the windows system.

It was tested against the current test suite.

Resolves: #590

Author: dariuszparys

testinfra/modules/systeminfo.py

@@ -29,7 +29,7 @@ def sysinfo(self):
             "arch": None,
         }
         uname = self.run_expect([0, 1], 'uname -s')
-        if uname.rc == 1:
+        if uname.rc == 1 or uname.stdout.lower().startswith("msys"):
             # FIXME: find a better way to detect windows here
             sysinfo.update(**self._get_windows_sysinfo())
             return sysinfo