Fix crash issue for path animation and path interpulator

Fix crash issue for path animation and path interpulator

When set progress value out of [0,1], path animation and
path interpulator should make sure the value be modified
in the valid value range, otherwise the QQuickPath::backwardsPointAt()
will crash.

Task-number: QTBUG-24308
Change-Id: Icd6e9165c9f844ddb8ec84c229eac4db5246a749
Reviewed-by: Michael Brasser <michael.brasser@nokia.com>