Godot: Omni light dual paraboloid shadows are broken

[fracteed]

Operating system or device, Godot version, GPU Model and driver (if graphics related):
Win10 current Godot 3 build

Issue description:
When changing the shadow mode on an omni light from Cube to Dual Paraboloid, the shadow disappears. If you increase the Shadow>contact amount from the default 0, the shadow does start to appear but looks very incorrect.

Not sure exactly when this broke, but I tried this on a build from about a month ago and it looks correct:

And here is the same scene on a current build. The dual paraboloid shadow light is on the right:

Steps to reproduce:

Link to minimal example project:

omni_shadow_bug.zip

[reduz]

Can you (or anyone else) bisect? that would be highly appreciated.

[ghost]

284f8f6

commit 284f8f6d91d7c9663fe8b25aa652265579b412a6
Author: Chaosus
Date:   Sat Nov 25 23:18:01 2017 +0300

    Fixed invalid transform when skip_vertex_transform used