EX-4052 tests: use stack_trap within a subtest in sanity-lipe

EX-4052 tests: use stack_trap within a subtest in sanity-lipe

Trap in a subshell is handled differently across bash versions.
This patch moves stack_trap into subtests to make them work
reliably.

Test-Parameters: trivial clientdistro=el7.9 testlist=sanity-lipe
Test-Parameters: trivial clientdistro=el8.4 testlist=sanity-lipe

Lustre-change: https://review.whamcloud.com/45889
Lustre-commit: db8e16fd8434651ed6102a6be79828346775f87e

Change-Id: I00eac5a8cf9511c8e1e531eb54f52ce443e5f77e
Signed-off-by: Jian Yu <yujian@whamcloud.com>
Reviewed-by: John L. Hammond <jhammond@whamcloud.com>
Reviewed-on: https://review.whamcloud.com/46026
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>