V4S: Customer code can throw off V4S trigger calculations

[davidhabib]

We've had a few customers reporting that their Total Volunteers statistics on a shift get out of sync with the actual Volunteer Hours. One customer was able to pinpoint when it happened, due to their own workflow also updating the Hours. We should investigate whether we can make the V4S trigger(s) more robust to deal with being called multiple times in the same context.

from Peter Allen (Geva Theatre Center, Inc.)

1. I've created additional custom fields on the Hours object: Position (pick-list), Grade (pick-list), Requires Followup (checkbox), and Venue (formula).
2. When an Hour record is created, the Grade is defaulted to "Meets Expectations."
3. When a Volunteer changes their Hour.Status from Confirmed to Cancelled, the Total Volunteers roll up was triggered.
4. The roll up was then also triggered (I assume) by a Workflow rule that I had in place, which changed the Grade field to blank upon the Hour.Status being changed to Cancelled.
5. Once I deactivated this workflow, the problem of the roll up "double dipping" disappeared.

[davidhabib]

**lurch: add

[LurchTheButler]

Tracking W-022349