Better collada doesn't properly export when there's several armatures on the same mesh

I have a female character, the body is rigged with the blender default human rig, and the hair of her is rigged with another armature parented to the head bone.

[azuka.new.zip](https://github.com/godotengine/collada-exporter/files/2425996/azuka.new.zip)

It works great on blender, but when I export to godot the hair doesn't become parented properly.

I already tried to test this on unity as well and the same problem appears, it seems is not just a godot issue.