LU-17975 tests: execvp error on file write_append_truncate

LU-17975 tests: execvp error on file write_append_truncate

test fails on sles15sp4 clients due to write_append_truncate
not found:
  execvp error on file write_append_truncate
    (No such file or directory)

HPE-bug-id: LUS-8427
Test-Parameters: trivial testlist=parallel-scale env=ONLY=write_append_truncate
Signed-off-by: Elena Gryaznova <elena.gryaznova@hpe.com>
Reviewed-by: Alexander Boyko <alexander.boyko@hpe.com>
Reviewed-by: Alexander Zarochentsev <alexander.zarochentsev@hpe.com>
Change-Id: I88a5a6c30510dff19b59d32eca2a90566a21f64e
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/55530
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>