frameworks: disable loading notification groups in System profiles

While the functionality of groups was left in the ProfileManager
backend, the front end no longer exists, and there were default
notification groups still being loaded. Remove the default ones and do
not load any that may have been persisted.

Change-Id: I4e4102607f1380d6fc5f6be7746d06bebf3c006b
Signed-off-by: Roman Birg <roman@cyngn.com>