Remove redundant future retry [RHELDST-9679]

Originally, the fast purge client would retry failed futures. Now with
the HTTP retries it doesn't make sense to have both. The interaction
between the two causes failing purges to run much longer than the
desired 5 minutes.

This change removes the Future retry in favour of the urllib3 retry.

fastpurge/_client.py

@@ -173,7 +173,6 @@ def __executor(self):
                         sync(name="fastpurge").\
                         with_poll(self.__poll_purges).\
                         with_throttle(count=self.MAX_REQUESTS).\
-                        with_retry().\
                         with_cancel_on_shutdown()
         return self.___executor