ui/vcslider: another attempt to fix a rendering deadlock
ui/vcslider: another attempt to fix a rendering deadlock

Basically this change requests an update of the shadow level bar only when the monitoring value changes

nedmech/qlcplus,sbenejam/qlcplus,kripton/qlcplus,nedmech/qlcplus,plugz/qlcplus,kripton/qlcplus,mcallegari/qlcplus,mcallegari/qlcplus,nedmech/qlcplus,sbenejam/qlcplus,plugz/qlcplus,sbenejam/qlcplus,nedmech/qlcplus,sbenejam/qlcplus,mcallegari/qlcplus,sbenejam/qlcplus,plugz/qlcplus,plugz/qlcplus,nedmech/qlcplus,plugz/qlcplus,mcallegari/qlcplus,kripton/qlcplus,kripton/qlcplus,nedmech/qlcplus,plugz/qlcplus,mcallegari/qlcplus,kripton/qlcplus,kripton/qlcplus,plugz/qlcplus,kripton/qlcplus,sbenejam/qlcplus,mcallegari/qlcplus,sbenejam/qlcplus,mcallegari/qlcplus