Remove IPv6 binding.

IPv6 binding fails on my machine, which prevents startup and leaves the
node using 100% CPU on a core. Pending implementing graceful binding
failure, this seems sufficient for now.

jvm 1    | WARN  - AbstractLifeCycle          - FAILED SocketConnector@0:0:0:0:0:0:0:1:8080: java.net.SocketException: Protocol family unavailable
jvm 1    | java.net.SocketException: Protocol family unavailable
jvm 1    |  at java.net.PlainSocketImpl.socketBind(Native Method)
jvm 1    |  at java.net.AbstractPlainSocketImpl.bind(AbstractPlainSocketImpl.java:376)
jvm 1    |  at java.net.ServerSocket.bind(ServerSocket.java:376)
jvm 1    |  at java.net.ServerSocket.<init>(ServerSocket.java:237)
jvm 1    |  at org.eclipse.jetty.server.bio.SocketConnector.newServerSocket(SocketConnector.java:91)
jvm 1    |  at org.eclipse.jetty.server.bio.SocketConnector.open(SocketConnector.java:80)
jvm 1    |  at org.eclipse.jetty.server.AbstractConnector.doStart(AbstractConnector.java:311)
jvm 1    |  at org.eclipse.jetty.server.bio.SocketConnector.doStart(SocketConnector.java:151)
jvm 1    |  at org.eclipse.jetty.util.component.AbstractLifeCycle.start(AbstractLifeCycle.java:59)
jvm 1    |  at org.eclipse.jetty.server.Server.doStart(Server.java:273)
jvm 1    |  at org.eclipse.jetty.util.component.AbstractLifeCycle.start(AbstractLifeCycle.java:59)
jvm 1    |  at freenet.winterface.core.ServerManager.startServer(ServerManager.java:104)
jvm 1    |  at freenet.winterface.core.WinterfacePlugin.runPlugin(WinterfacePlugin.java:78)
jvm 1    |  at freenet.pluginmanager.PluginHandler$PluginStarter.run(PluginHandler.java:66)
jvm 1    |  at java.lang.Thread.run(Thread.java:724)