Clear txcount on enroll

The transaction count on 'join' was being honored as high, when
it never should be.

confluent_server/confluent/collective/manager.py

@@ -227,6 +227,7 @@ def handle_connection(connection, cert, request, local=False):
             f = open('/etc/confluent/cfg/myname', 'w')
             f.write(name)
             f.close()
+            cfm.clear_configuration()
             eventlet.spawn_n(connect_to_leader, rsp['collective']['fingerprint'], name)
     if 'enroll' == operation:
         #TODO(jjohnson2): error appropriately when asked to enroll, but the master is elsewhere

confluent_server/confluent/config/configmanager.py

@@ -497,8 +497,10 @@ def stop_leading():
 
 def clear_configuration():
     global _cfgstore
+    global _txcount
     _cfgstore = {}
     todelete = _config_areas + ('globals', 'collective', 'transactioncount')
+    _txcount = 0
     for cfg in todelete:
         try:
             os.remove(os.path.join(ConfigManager._cfgdir, cfg))