ext/services: allow for os=Linux feature request from VM

It's weird to set it for Windows, but not Linux.

qubes/ext/windows.py

@@ -34,7 +34,7 @@ class WindowsFeatures(qubes.ext.Extension):
 
         guest_os = None
         if 'os' in untrusted_features:
-            if untrusted_features['os'] in ['Windows']:
+            if untrusted_features['os'] in ['Windows', 'Linux']:
                 guest_os = untrusted_features['os']
 
         qrexec = None

qubes/tests/ext.py

@@ -213,7 +213,7 @@ class TC_10_WindowsFeatures(qubes.tests.QubesTestCase):
                 'version': '1',
                 'default-user': 'user',
                 'qrexec': '1',
-                'os': 'Linux'})
+                'os': 'other'})
         self.assertEqual(self.vm.mock_calls, [])
 
 class TC_20_Services(qubes.tests.QubesTestCase):