LU-17057 tests: Fix sanity-sec/0

LU-17057 tests: Fix sanity-sec/0

Command executed through 'runas' on failure breaks
out of running test script. While this failure is
expected. The setting of 'set -e' forces the pipeline
to exit the running script immediately. This patch
fixes this by checking the return value and then
taking the appropriate action.

This patch also fixes 'touch' command to file f4 by
correctly calling it via uid and gid as it was set
few lines above.

Lustre-change: https://review.whamcloud.com/53194
Lustre-commit: 0b5e252d973e00200660a81f1cdb440f8f4f1886

Test-Parameters: trivial testlist=sanity-sec env=ONLY=0,ONLY_REPEAT=100
Signed-off-by: Arshad Hussain <arshad.hussain@aeoncomputing.com>
Change-Id: I06e6d22840e31add8c24cf90c31b98464d580ae7
Reviewed-by: Sebastien Buisson <sbuisson@ddn.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-on: https://review.whamcloud.com/c/ex/lustre-release/+/53439
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>