Add list of clusters and nodes


mysql-test/lib/mtr_process.pl:
  Start servers in parallell
mysql-test/lib/mtr_report.pl:
  Report about number of restarts
mysql-test/lib/mtr_stress.pl:
  Update args to pass to mysqld_start
mysql-test/mysql-test-run.pl:
  Start servers in  parallell
  Add lists for clusters and it's nodes to keep track of things