Replace deprecated tenacity.Retrying.call

... by the __call__ method following the deprecation in the tenacity
library[1].

[1] d66af82a70

Change-Id: Ib2934ff730f99e1a777c106f2c41a73b1cae3d27

os_brick/utils.py

@@ -62,7 +62,7 @@ def retry(exceptions, interval=1, retries=3, backoff_rate=2):
                 retry=tenacity.retry_if_exception_type(exceptions),
                 wait=tenacity.wait_exponential(
                     multiplier=interval, min=0, exp_base=backoff_rate))
-            return r.call(f, *args, **kwargs)
+            return r(f, *args, **kwargs)
 
         return _wrapper