When an overlength path is set as the temporary directory for test
case sys/audit/inter-process:shm_unlink_success, the test will fail,
e.g.
```
root@freebsd:/usr/tests/sys/audit # env TMPDIR=/var/tmp/tests/kyua kyua test inter-process:shm_unlink_success
inter-process:shm_unlink_success -> failed: shm_unlink.*fileforaudit.*return,success not found in auditpipe within the time limit [10.452s]
Results file id is usr_tests_sys_audit.20220412-221852-924310
Results saved to /root/.kyua/store/results.usr_tests_sys_audit.20220412-221852-924310.db
0/1 passed (1 failed)
```
The root cause is that dirpath is defined too small to handle it.
Reviewers: vangyzen, dab
Differential Revision: https://reviews.freebsd.org/D34885
Submitted by: Yongbo Yao (yongbo.yao@dell.com)
Sponsored by: Dell Technologies
This was correct in the final version on Phabricator, but somehow I screwed
up applying the patch locally.
Reported by: linimon
Pointy-hat-to: asomers
MFC after: 2 weeks
X-MFC-With: 335307
