HAMMER VFS - Hack cursor iterator when unlocked cursor moved to parent
* It is possible to reverse-index a cursor while it is unlocked due to
a node deletion moving cursors on that node to the parent, and a
subsequent insertion then inserting new elements between the cursor's
current position and its expected iteration range.
* Detect the case with a new flag (hack!) HAMMER_CURSOR_ITERATE_CHECK
and just iterate past the elements outside the iteration range in
this case.
Reported-by: YONETANI Tomokazu <qhwt+dfly@les.ath.cx>