Don't increment the record number until after reviewing the record,
otherwise we might choose the wrong record (not part of the test case,
found by inspection).

When I switch the overflow tracking code recently, I introduced a bug
in column store where we'd not check overflow records when we should,
and vice-versa, this was found by the test case.
If we have "missing" records flagged by salvage, and we're not skipping
records from the page, and the first record we're taking from the page
is a "delete", we have to merge them, otherwise the RLE count won't be
optimal and verify will complain.
We can overwrite the first block when corrupting the file, force the
salvage so that's ignored.