LU-13776 tests: make sure pjdfstest.sh writes to tmp

LU-13776 tests: make sure pjdfstest.sh writes to tmp

no writes to random Lustre source locations as they could be readonly

Test-Parameters: trivial
Test-Parameters: fstype=ldiskfs testlist=pjdfstest
Test-Parameters: fstype=zfs testlist=pjdfstest
Change-Id: Icd262a698390eadf4b53cd5d311bc6c2a561a79e
Signed-off-by: Oleg Drokin <green@whamcloud.com>
Reviewed-on: https://review.whamcloud.com/39338
Reviewed-by: James Nunez <jnunez@whamcloud.com>
Reviewed-by: Wei Liu <sarah@whamcloud.com>
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>