`render-templates -d` is used to remove all files that it previously
generated, so that it is easy to look around during development.

But, probably due to oversight, it was only *tdd files, that were
removed, with *fdd generated files still left in place.

-> Fix it.

The list of generated files, that is now additionally removed after this patch is:

        instance-fdd-enb-input-schema.json
        instance-fdd-gnb-input-schema.json
        instance-fdd-lopcomm-enb-input-schema.json
        instance-fdd-lopcomm-gnb-input-schema.json
        instance-fdd-lopcomm-ue-lte-input-schema.json
        instance-fdd-lopcomm-ue-nr-input-schema.json
        instance-fdd-ors-enb-input-schema.json
        instance-fdd-ors-gnb-input-schema.json
        instance-fdd-ors-ue-lte-input-schema.json
        instance-fdd-ors-ue-nr-input-schema.json
        instance-fdd-ue-lte-input-schema.json
        instance-fdd-ue-nr-input-schema.json
        software-fdd-lopcomm.cfg
        software-fdd-lopcomm.cfg.json
        software-fdd-ors.cfg
        software-fdd-ors.cfg.json
        software-fdd.cfg
        software-fdd.cfg.json
        test/testFDD-LOPCOMM.py
        test/testFDD-ORS.py
        test/testFDD.py

/cc @tomo, @xavier_thompson, @Daetalus
/reviewed-by @jhuge, @lu.xu
/reviewed-on nexedi/slapos!1463