Remove reduntant call to update_instance_info_cache

get_instance_nw_info calls _get_instance_nw_info,
which is decorated with @refresh_cache. This in
turn calls update_instance_info_cache, again. This
is both expensive and more importantly dangerous because
the method update_instance_info_cache may call
_get_instance_nw_info itself, thus causing an infinite
loop.

Change-Id: Id8f0241d1c6609cf4e064ee6855228ae7de250e2
Partial-bug: 1235435

nova/network/neutronv2/api.py

@@ -447,8 +447,6 @@ def get_instance_nw_info(self, context, instance, networks=None):
            and update cache.
         """
         result = self._get_instance_nw_info(context, instance, networks)
-        update_instance_info_cache(self, context, instance, result,
-                                   update_cells=False)
         return result
 
     @refresh_cache