Schedules the I/O as soon as possible (i.e. after all sources have been read)
Schedules the I/O as soon as possible (i.e. after all sources have been read)

One significant consequence is that now when an object is stored in a split branch
the rule is associtated with the branch of the last of the rule's sources rather
than the last of the object's data member.

This fixes: ROOT-7009

tc3t/qoot,tc3t/qoot,tc3t/qoot,tc3t/qoot,tc3t/qoot,tc3t/qoot,tc3t/qoot,tc3t/qoot,tc3t/qoot,tc3t/qoot