TabPane fails to initialize in a background thread when adding a series, throwing a ConcurrentModificationException.

To reproduce, use the newly developed NodeInitializationStressTest:

```
    @Test
    public void tabPane() {
        test(() -> {
            TabPane c = new TabPane();
            c.setSkin(new TabPaneSkin(c));
            c.getTabs().setAll(createTabs());
            return c;
        }, (c) -> {
            c.getTabs().setAll(createTabs());
            accessControl(c);
        });
    }
```

Exception:

java.util.ConcurrentModificationException
at java.base/java.util.AbstractList$Itr.checkForComodification(AbstractList.java:401)
at java.base/java.util.AbstractList$Itr.next(AbstractList.java:370)
at javafx.base/com.sun.javafx.collections.VetoableListDecorator$VetoableIteratorDecorator.next(VetoableListDecorator.java:706)
at javafx.controls/javafx.scene.control.skin.TabPaneSkin$TabHeaderArea.getTabHeaderSkin(TabPaneSkin.java:1033)
at javafx.controls/javafx.scene.control.skin.TabPaneSkin$TabHeaderArea.removeTab(TabPaneSkin.java:1017)
at javafx.controls/javafx.scene.control.skin.TabPaneSkin.lambda$8(TabPaneSkin.java:518)
at javafx.graphics/javafx.animation.Animation.runHandler(Animation.java:1147)
at javafx.graphics/javafx.animation.Animation.finished(Animation.java:1141)
at javafx.graphics/javafx.animation.AnimationAccessorImpl.finished(AnimationAccessorImpl.java:49)
at javafx.graphics/com.sun.scenario.animation.shared.SingleLoopClipEnvelope.timePulse(SingleLoopClipEnvelope.java:107)
at javafx.graphics/javafx.animation.Animation.doTimePulse(Animation.java:1234)
at javafx.graphics/javafx.animation.Animation$1.timePulse(Animation.java:190)
at javafx.graphics/com.sun.scenario.animation.AbstractPrimaryTimer.timePulseImpl(AbstractPrimaryTimer.java:316)
at javafx.graphics/com.sun.scenario.animation.AbstractPrimaryTimer$MainLoop.run(AbstractPrimaryTimer.java:239)
at javafx.graphics/com.sun.javafx.tk.quantum.QuantumToolkit.pulse(QuantumToolkit.java:588)
at javafx.graphics/com.sun.javafx.tk.quantum.QuantumToolkit.pulse(QuantumToolkit.java:572)
at javafx.graphics/com.sun.javafx.tk.quantum.QuantumToolkit.pulseFromQueue(QuantumToolkit.java:565)
at javafx.graphics/com.sun.javafx.tk.quantum.QuantumToolkit.lambda$6(QuantumToolkit.java:346)
at javafx.graphics/com.sun.glass.ui.InvokeLaterDispatcher$Future.run(InvokeLaterDispatcher.java:95)

## Root Cause
Animation gets started in a background thread, which causes the animation handler to run in the FX application thread, thus creating simultaneous access to the control's fields (list of children in this case).

## Solution
Skip the animation.