user settings - "reset settings" behaves differently on web-ui and webadmin concerning the properties removal/replacement issue

[sgratch]

When the user invokes 'reset settings' via the admin portal - all currently supported webadmin properties (except SSH_PUBLIC_KEY) are removed.
When the user invokes 'reset settings' via the vm portal - all currently supported vmportal properties (except SSH_PUBLIC_KEY and webadmin (grids setting)) are removed and then re-created with a new default value.

It's better to keep a consistent behavior for both portals and remove all properties after reset.

This was originally raised here: oVirt/ovirt-engine#132 (review)