Trac Ticket #335 - transaction retries need to be cache aware
    
    https://fedorahosted.org/389/ticket/335
    
    Fix description:
    When libdb returns DEADLOCK and backend update function retries
    the operation, the target entry is reset to the original shape.
    The target entry might be or might not be in the entry cache.
    Regardless of the status, the original code just releases the
    entry with backentry_free before going into the next loop, which
    causes the cache error.
    
    This patch checks the status of the entry. If it is in the entry
    cache, it removes it from the entry cache and adds a new entry
    back to the cache if necessary. To get the accurate cache status
    of each entry, the output argument cache_res to id2entry_add_ext
    is added.
    
    Additinally, error checking for the conflict value in index_add_mods
    was week (curr_attr). This patch is adding the check.