Validate the dirty flag before saving preferences in each modules

Pressing apply button is applicable to all settings module, not only
for the one that is visible. Unless we do a validation before we save
preferences, other module can cause incorrect (old) preferences to be
saved.

Bug: 56885
Change-Id: I31df2ee0bf8b600a94e8fed1a784daf529186b16
Merge "Validate the dirty flag before saving preferences in each modules"