Make smd termination, both voluntary and involuntary robust and clean.
Remove deprecated process_model_queue
Cleanup imports in smd
Change service status model to include a count and increment the count with
updated ts when there's no change in status of the service from the previous update.
Don't insert new status row for a service if the status has not changed
since the prev check. Do create new rows when rockstor starts and when the
status changes. At other times, just update the ts and count.