In connect point mode, IgmpProxy cannot packet-out to the agg.device in slave mode

In connect point mode, IGMP packets are sent to the configured connect point. Consider a topology that consists of an ONOS cluster including two instances, one OLT, and one aggregation device.
Suppose that the connection point is configured as the upstream port of the agg.device. The first ONOS instance is the master of the OLT, and the second one is the master of the agg.device.  When an upstream IGMP packet arrives at instance1, IgmpProxy should forward it to the agg.device's upstream port. However, the packet cannot be forwarded to the connect point since instance1 is not the master of the agg.device. IgmpProxy performs a mastership check before packet-out a packet to a device. To solve the problem, the mastership check can be removed from the IgmpSender. The emit() method of PacketManager already checks the mastership of a device and dispatches a packet to the correct instance accordingly.