Update W3C supported handle to use response instead of looking at cap…

…abilities

Check the response back from a W3C conformant remote end for status key on
the response.

py/selenium/webdriver/remote/webdriver.py

@@ -179,7 +179,8 @@ def start_session(self, desired_capabilities, browser_profile=None):
         self.capabilities = response['value']
 
         # Quick check to see if we have a W3C Compliant browser
-        self.w3c = "specificationLevel" in self.capabilities
+        if response.get('status') is None:
+            self.w3c = True
 
     def _wrap_value(self, value):
         if isinstance(value, dict):