row-search releases "child" on error, and we were updating "child" to
point to pages that were the wrong pages to release on error. The code
in row-random and column-search don't require the same changes, but I
made them so the code continues to look roughly the same in all three
functions.
Merge pull request #1232 from wiredtiger/cleanup-row-search-error-handling

Fix row-search error handling.