BabuDB/Java/Replication:

changed the configuration of the test configuration to support MasterOnly instead of NoRestriction policy;
enhanced the heartbeatThread by simplifying its implementation; 
changed the maximal delay between two heartbeats from 10 to one second to meet the failover processing deadline;
fixed a bug to prevent deadlocks on master failover;
added a queue to buffer proxy RPCs while a failover is in progress;

git-svn-id: https://babudb.googlecode.com/svn/trunk@437 d4c7dd96-b7b2-11dd-893d-d98698f66bbf