Allow to set another other_entity name
    
    Association table's add, del commands needs as option list of cn of
    other_entity, which is added or deleted. There is a case (currently in vaults)
    that the name of option is different than the name of other_entity.
    In this situation we can set 'other_option_name' and put there the option name.
    This option name will be used instead of 'other_entity' name.
    
    Part of: https://fedorahosted.org/freeipa/ticket/5426
    
    Reviewed-By: Martin Basti <mbasti@redhat.com>
    Reviewed-By: Petr Vobornik <pvoborni@redhat.com>