Issues editing H5P content when local_metadata plugin is installed

[mhughes2k]

We have recently started using H5P content on a server that also is using the local_metadata plugin to provide additional hooks on to module edit form.

The H5P module edit form works correctly when creating an instance, but when editing an instance it comes back with an "invalidhvp" error.

This error has been identified and captured as a ticket in the moodle-local_metadata plugin's tracker: https://github.com/PoetOS/moodle-local_metadata/issues/24

However the suggestion is that H5P is expecting an $instance->instance variable, and not the $instance->id, and that this isn't consistent with the "normal" structure (see comment on https://github.com/PoetOS/moodle-local_metadata/issues/18#issuecomment-526943039)