Bug 676053 - export task followed by import task causes cache assertion
    
    https://bugzilla.redhat.com/show_bug.cgi?id=676053
    
    Description: There were 3 places where an entry was not released
    by CACHE_RETURN (== not decrementing refcnt).  If an entry has
    positive refcnt in the entry cache, it won't be freed even if
    the entry never be accessed again.
    1. When a search request with VLV and/or SORT control failed.
    2. When comparing entries in compare_entries_sv (sort.c), and the
       second entry was not found, the first entry was not released.
    3. vlv_trim_candidates_byvalue (vlv.c) retrieves entries for
       performing binary search over the candidate list and put them
       into the cache.  They were not released.
    
    This patch adds CACHE_RETURN call for the above cases.