Skip tarfs regression test if module doesn't exist

[olivier]

Summary

When building customized FreeBSD without tarfs module, this regression test fail because
it can't load the module.

Test Plan

 mv /boot/kernel/tarfs.ko /boot/kernel/tarfs.ko.bak
# kyua test sys/fs/tarfs/
sys/fs/tarfs/tarfs_test:tarfs_basic  ->  skipped: This test requires tarfs and could not load it  [0.020s]
sys/fs/tarfs/tarfs_test:tarfs_notdir_device  ->  skipped: This test requires tarfs and could not load it  [0.020s]
sys/fs/tarfs/tarfs_test:tarfs_notdir_dot  ->  skipped: This test requires tarfs and could not load it  [0.019s]
sys/fs/tarfs/tarfs_test:tarfs_notdir_dotdot  ->  skipped: This test requires tarfs and could not load it  [0.019s]
sys/fs/tarfs/tarfs_test:tarfs_notdir_file  ->  skipped: This test requires tarfs and could not load it  [0.019s]

Results file id is usr_tests.20230228-200204-811621
Results saved to /root/.kyua/store/results.usr_tests.20230228-200204-811621.db

5/5 passed (0 failed)

[ngie]

The kldload check function seems like it should be in a common function. Also: I might reword the message to state: “This test requires the tarfs kernel module (not available).”

tests/sys/fs/tarfs/tarfs_test.sh

51

Should this use umount -f ?

[ngie]

tests/sys/fs/tarfs/tarfs_test.sh

51

Or maybe a different sanity check to run beforehand, like ‘test -d “${mnt}”’?

[olivier]

In D38828#884135, @ngie wrote:

The kldload check function seems like it should be in a common function. Also: I might reword the message to state: “This test requires the tarfs kernel module (not available).”

About the "not available", I didn't add this precision because in some case it could be a loading failure too (like a child module not available).