java plugin: Wait with the configuration until the daemon has forked.

java plugin: Wait with the configuration until the daemon has forked.

Passing the configuration to Java-based plugins requires the JVM to be
active and running. However, the JVM starts some threads that are lost
when the daemon forks to the background.

This patch changes the behavior of the Java plugin to copy the
configuration blocks found to a local variable and run the configuration
of the Java-based plugins from the `init' callback, because it is
invoked after the daemon has forked to the background.