ensure composite refresh handler synced w/ mutable composite

ensure composite refresh handler synced w/ mutable composite

Fixed issue where the :class:`_mutable.MutableComposite` construct could be
placed into an invalid state when the parent object was already loaded, and
then covered by a subsequent query, due to the composite properties'
refresh handler replacing the object with a new one not handled by the
mutable extension.

Fixes: #6001
Change-Id: Ieebd8e6afe6b65f8902cc12dec1efb968f5438ef