Assuming you have already upgrade your DB during first cell upgrade using upgrade script /opt/vmware/vcloud-director/bin/upgrade
Run bin file with response.properties file (of first cell which is already upgraded).
./ vmware-vcd-5.5.1...bin -r response.properties. at end you might asked for DB upgrade. DON'T PERFORM IT, as your database is already upgraded during first cell upgrade.
this will upgrade only your cell binaries to 5.5u1.