QValidator doesn't notify when it's validation criteria changes so is
susceptible to order of evaluation issues.  Deferring the initial
validation will ensure validators with static criteria are correctly
applied.  Notification from QValidator on changes would solve this
for all cases: QTBUG-23694.

Task-number: QTBUG-21103
Change-Id: I920f36645fd18ce809db56b5daf73545f1d603dc
Reviewed-by: Martin Jones <martin.jones@nokia.com>