Fix regressions introduced by 914888.
On the other hand, Corona::addItem indirectly calls Containment::itemChange,
which ends up calling AppletPrivate::mainConfigGroup, which then creates a config
group in the wrong file (plasmarc) because isContainment was not set.
This also caused a regression where removed applets reappeared on next plasma run.
Fix:
Manually set isContainment before adding the item to the corona, then
call setIsContainment with a new argument to force the initialization.
svn path=/branches/KDE/4.2/kdelibs/; revision=927891
6ebe8f0b9f