If containment plugin is provided in the shell package's defaults file
then use it instead of defaulting to desktopcontainment
BUG: 348617
FIXED-IN: 5.4
REVIEW: 123990
The backing class ConfigGroup opens config files in KConfig::FullConfig
by default, which prevents syncs when a desktop init script tries to
adapt the shell's appletsrc file, as Corona opens in SimpleConfig mode.
This reuses Corona's instance when the appletsrc is opened, fixing the
script and making the shell behave consistently around its config file.
all scripts in the folder
$prefix/share/org.kde.plasma.desktop/updates will
be correctly executed now
(other shell packages will have their name instead of
org.kde.plasma.desktop)
even when they are created in the standaloneappcorona, create the containment
so when the same appletsrc is loaded in the full shell mode it works as expected
no warning message about unknown service anymore
panel can be loaded from a template again, so the
"add default panel" option can get reimplemented now