ScrollContainer's "Ignore" mouse filter doesn't work as expected, does the same as "Stop"

[mthreis]

Godot version:
3.0.2

OS/device including version:
Windows 10

Issue description:
If set to "Ignore", the ScrollContainers' mouse filter will still get mouse click events and be able to be dragged with it, unlike VScrollBars.

Steps to reproduce:

1. Add a ScrollContainer node to the scene.
2. Add a VBoxContainer to it, with some labels as children.
3. Set the mouse filter to Ignore and see that it works the same as Stop.