ceph: do not print the whole xattr value if it's too long

If the xattr's value size is long enough the kernel will warn and
then will fail the xfstests test case.

Just print part of the value string if it's too long.

At the same time fix the function name issue in the debug logs.

Link: https://tracker.ceph.com/issues/58404


Signed-off-by: Xiubo Li <xiubli@redhat.com>
Reviewed-by: Ilya Dryomov <idryomov@gmail.com>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>