Script node plugs are not cleaned when calling 'load'

[manuelito02]

Version: Gaffer 1.3.9.0-linux
Third-party tools: n/a
Third-party modules: n/a

Description

When calling 'load' on a script node, it seems that existing plugs are not removed. We have in particular issues with 'defaultFormat' and 'openColorIO' that accumulate each time when we 'load' a Gaffer script.

Steps to reproduce

Open a new Gaffer and execute following code:

path = "/tmp/empty.gfr"
root["fileName"].setValue(path)
root.save()
root.load()

Each time you execute the last line, you'll end up with another pair of 'defaultFormat' and 'openColorIO' plugs: