ext4/048: skip test of filename wipe if journal checkpoint is not supported

ext4/048: skip test of filename wipe if journal checkpoint is not supported

ext4/048 will fail when running on older kernels that don't support
the filename wipe feature.  The journal checkpoint ioctl is a related
feature, and landed just a little bit after filename wipe feature, so
use support for the journal checkpoint ioctl as a proxy for support
for the filename wipe feature.

Without this change, this test will fail when tesing 5.10, 5.4, and
other LTS kernels.

Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Cc: Leah Rumancik <leah.rumancik@gmail.com>
Tested-by: Yang Xu <xuyang2018.jy@fujitsu.com>
Reviewed-by: Leah Rumancik <leah.rumancik@gmail.com>
Signed-off-by: Eryu Guan <guaneryu@gmail.com>