Changes in integration-rabbitmq and mule-transport-rabbitmq to support connection to last used rabbit mq connection. 

Changes have been made in inntegration-rabbitmq and mule-transport-rabbitmq to support connection to last used rabbit mq connection. If the last used rabbit mq connection fails then connection is tried on a round robin basis and on successful connection this connection is remembered and used in the future. If connections to all configured connections fail then an exception is thrown. These changes will be particularly useful in case of a rabbit mq cluster where the client has to connect to another live rabbit mq node when the connected node goes down.