FX needs to install additional finish listener to prevent FX shutdown

This issue is created as a follow-up FX bug for
https://bugs.openjdk.java.net/browse/JDK-8043303 (FX application fails to get loaded after accept authentication dialog)

FX runtime will shutdown after authentication dialog is closed and app hangs at startup as FX application is terminated.

A solution is that FX patch installs additional finish listener - the listener also prevent FX shutdown and the lifetime of the listener is between FX toolkit warmup and first request to create FX applet's adapter. This way, we don't change the implicitExit attribute internally and it remains under application control.