correctly return error in nsiservice if connection with specified id already exists
correctly return error in nsiservice if connection with specified id already exists

jab1982/opennsa,jeroenh/OpenNSA,NORDUnet/opennsa,jeroenh/OpenNSA,jeroenh/OpenNSA,NORDUnet/opennsa,jab1982/opennsa,NORDUnet/opennsa