Bug 676053 - export task followed by import task causes cache assertion
    
    https://bugzilla.redhat.com/show_bug.cgi?id=676053
    
    Description: When Simple Paged Results is requested and a page is
    returned, one entry is read ahead to check whether more entries
    exist or not.  The read-ahead retrieves an entry (if any) and adds
    it into the entry cache.  Simple Paged Results code puts the read-
    ahead entry back, but there was missing to call cache_return for
    the entry (that decrementing refcnt).  If ldif2db.pl is called with
    the cache state, it finds out the entry which is still referred.
    This patch calls cache_return when the Simple Paged Results puts
    the read-ahead entry back.  Plus, adding a debug function dump_hash.