#2 Server does not shutdown properly

[Brett Wooldridge]

The stopServer() method of DHCPCoreServer needs to include the following:

this.threadPool.shutdownNow();

As noted in bug#2034928 opened by user stanbey, if the DHCPCoreServer were extendable (for example, the constructor was not private), this would have been easy to address without modifiying the original code.