[Fix] Rewrite WorkComplete Frame to Request

According to the protocol documentation and your code:

https://github.com/gearman/gearmand/blob/master/PROTOCOL#L76

https://github.com/johnewart/gearman-java/blob/12aacea06020e058b9ab071ab90c3c6f9cabd83b/gearman-common/src/main/java/net/johnewart/gearman/constants/PacketType.java#L24

WorkComplete for Worker should be Request not Response. This pull request is resolving problem with using PHP or Python clients for Java Workers.