change output format in cluster_mpib.cu to avoid trailing whitespaces
change output format in cluster_mpib.cu to avoid trailing whitespaces

feltor-dev/feltor,feltor-dev/feltor,mwiesenberger/feltor,mwiesenberger/feltor,mwiesenberger/feltor,feltor-dev/feltor,mwiesenberger/feltor,feltor-dev/feltor