If a job was enqueued with a CellServiceConstraint (which is currently
only SMS jobs), then it'll never run until it gets service, even if you
flip the "enable SMS sending over wifi" toggle.
This has created bad situations in the past, where SMS jobs just get
stuck on devices that never report having cell service (like VM's or
wifi only devices).
This fixes it by *always* using NetworkOrCellServiceConstraint, and then
deciding whether a constraint is met by checking the "wifi SMS" setting
at decision-time.
310ec8f296