In row-search, release the held page if a leaf-only was not specified.

I think the test at the end of __wt_row_search is wrong, we're releasing the "current" page if leaf != NULL, and that's wrong, we should only release the current page if no leaf-page WT_REF was specified.

I think the safest test is to compare current against leaf, which is basically the same as leaf == NULL, in the current code.