dns: nsone: Make NsOneResponse lists instance variables

Make NSOneResponse.errors and NSOneResponse.objects instance variables,
rather than class variables.

This was found due to errors in NSOneDNSDriver unit testing that only
appeared when tests were run together, not when tests were run
individually.

Author: Aaron Sierra

libcloud/common/nsone.py

@@ -24,10 +24,10 @@
 
 
 class NsOneResponse(JsonResponse):
-    errors = []  # type: List[Dict]
-    objects = []  # type: List[Dict]
-
     def __init__(self, response, connection):
+        self.errors = []  # type: List[Dict]
+        self.objects = []  # type: List[Dict]
+
         super().__init__(response=response, connection=connection)
         self.errors, self.objects = self.parse_body_and_errors()
         if not self.success():