In the PageDB repair utility if a (key, value) pair in a page
does not belong on a page, then move it to the next page
only if the key does not already exist in the next page. If the
key already exists in the next page, then do not move the
(key, value) pair but delete the (key, value) pair.
Minor change to logging output so it will emit position i
of the key with respect to the original ordering of the keys.