feat(core): closed states instead of lost states (#573)

In order to be better in sync with the official documentation (https://zookeeper.apache.org/doc/r3.5.5/zookeeperProgrammers.html#ch_zkSessions) it is better to rename those variables to `close` instead of `lost`.

kazoo/client.py

@@ -68,7 +68,7 @@
 string_types = six.string_types
 bytes_types = (six.binary_type,)
 
-LOST_STATES = (KeeperState.EXPIRED_SESSION, KeeperState.AUTH_FAILED,
+CLOSED_STATES = (KeeperState.EXPIRED_SESSION, KeeperState.AUTH_FAILED,
                KeeperState.CLOSED)
 ENVI_VERSION = re.compile(r'([\d\.]*).*', re.DOTALL)
 ENVI_VERSION_KEY = 'zookeeper.version'
@@ -513,14 +513,14 @@ def _session_callback(self, state):
 
         # Note that we don't check self.state == LOST since that's also
         # the client's initial state
-        dead_state = self._state in LOST_STATES
+        closed_state = self._state in CLOSED_STATES
         self._state = state
 
         # If we were previously closed or had an expired session, and
         # are now connecting, don't bother with the rest of the
         # transitions since they only apply after
         # we've established a connection
-        if dead_state and state == KeeperState.CONNECTING:
+        if closed_state and state == KeeperState.CONNECTING:
             self.logger.log(BLATHER, "Skipping state change")
             return
 
@@ -529,8 +529,8 @@ def _session_callback(self, state):
                              "state: %s", state)
             self._live.set()
             self._make_state_change(KazooState.CONNECTED)
-        elif state in LOST_STATES:
-            self.logger.info("Zookeeper session lost, state: %s", state)
+        elif state in CLOSED_STATES:
+            self.logger.info("Zookeeper session closed, state: %s", state)
             self._live.clear()
             self._make_state_change(KazooState.LOST)
             self._notify_pending(state)