LU-18814 tests: run extra prog, execute NLOOPS mpi workloads

LU-18814 tests: run extra prog, execute NLOOPS mpi workloads

Patch adds the abilities:
  - execute the workload the specified number of times (NLOOPS)
    instead of execution them during the test duration set;
  - execute the mpi EXTRAPROG in addition to allowed now IOR,
    mdtest and simul;
  - execute more mpi instances than the number of clients in
    case if NLOOPS set.

Test-Parameters: trivial
Signed-off-by: Elena Gryaznova <elena.gryaznova@hpe.com>
HPE-bug-id: LUS-12231
Reviewed-by: Vladimir Saveliev <vladimir.saveliev@hpe.com>
Reviewed-by: Alexander Boyko <alexander.boyko@hpe.com>
Change-Id: I8e019560356edb94fee75cfcb55e86c6cc7bd69d
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/58410
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>