adaasync: Harmonize with daasync

We should call cam_periph_async() always, like SCSI does. This routine
is supposed to be more of a catch-all.

cam_periph_async() only does actions for AC_LOST_DEVICE. It ignores all
other events (today), but this may not always be true. So this is a nop
change.

Drop in a 'break' so we don't fall through unnecessarily.

Sponsored by: Netflix
Reviewed by: mav
Differential Revision: https://reviews.freebsd.org/D35057