PacketType of CantDo class is wrong

[hados99]

When create CantDo class instance with string parameter,
PacketType is setted to CAN_DO not CANT_DO.

https://github.com/johnewart/gearman-java/blob/master/gearman-common/src/main/java/net/johnewart/gearman/common/packets/request/CantDo.java

public CantDo(String function)
{
this.type = PacketType.CAN_DO;
this.functionName = new AtomicReference<>(function);
}

[cordje]

#10