Remove EVENT_STATUS_SAVE in favour for callback

Replace the EVENT_STATUS_SAVE with callback event.

Signed-off-by: Max Sikstrom <msikstrom@op5.com>
Remove EVENT_RETENTION_SAVE in faviour for callback event

Move check result logic from event.c to sretention.c, where the rest of
the rentention data code is placed

Signed-off-by: Max Sikstrom <msikstrom@op5.com>