Call updateVisibility() in ProgressManagerPrivate::init() to ensure that
it is really invisible when launching Qt Creator.

Also make sure that the opacity for the visible progress bar is 1.0
instead of 0.7 (which is the default opacity in QGraphicsOpacityEffect).

Task-number: QTCREATORBUG-16003
Change-Id: Ic268d903ce624c9e0b4c11e213002a22be1fba63
Reviewed-by: hjk <hjk@qt.io>