Compute requires_beating

Computers are smarter than humans. Proof is that we forgot to set
requires_beating to the etcd driver, whereas it does require it. Doh!
Same goes for Zookeeper actually.

Use the computer power to find out if a driver requires beating… or not.

Change-Id: I4ef5841a06fe361f87c3ba336d3688c3684bffd7

tooz/coordination.py

@@ -154,6 +154,9 @@ class CoordinationDriver(object):
         self._hooks_elected_leader = collections.defaultdict(Hooks)
         # A cache for group members
         self._group_members = collections.defaultdict(set)
+        self.requires_beating = (
+            CoordinationDriver.heartbeat != self.__class__.heartbeat
+        )
 
     def _has_hooks_for_group(self, group_id):
         return (len(self._hooks_join_group[group_id]) +

tooz/drivers/memcached.py

@@ -215,9 +215,6 @@ class MemcachedDriver(coordination._RunWatchersMixin,
     #: String used to keep a key/member alive (until it next expires).
     STILL_ALIVE = b"It's alive!"
 
-    #: This driver requires constant periodic (heart) beatings.
-    requires_beating = True
-
     def __init__(self, member_id, parsed_url, options):
         super(MemcachedDriver, self).__init__()
         options = utils.collapse(options)

tooz/drivers/redis.py

@@ -314,9 +314,6 @@ return 1
     .. _Lua: http://www.lua.org
     """
 
-    #: This driver requires constant periodic (heart) beatings.
-    requires_beating = True
-
     def __init__(self, member_id, parsed_url, options):
         super(RedisDriver, self).__init__()
         options = utils.collapse(options, exclude=self.CLIENT_LIST_ARGS)