Activate enforcement of Path type

This activates pre-prepared requirement of P to be of type Path<P>,
which had prerequisites in generated DTOs. Yangtools have been updated,
so it should be safe to activate this now.

Change-Id: I68ad3a77311e44db2e6bee1d7e2b3684090e5cbd
Signed-off-by: Robert Varga <rovarga@cisco.com>
Merge "Activate enforcement of Path type"