generic/052,4: filter out lost+found when running "ls $SCRATCH_MNT"

The generic/052 and generic/054 tests run ls on the root directory,
and on ext4 we have a lost+found directory which is not in the
golden output.

Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Reviewed-by: Eryu Guan <eguan@redhat.com>
Signed-off-by: Eryu Guan <eguan@redhat.com>

common/filter

@@ -401,5 +401,10 @@ _filter_mknod()
 	sed -e "s/mknod: [\`']\(.*\)': File exists/mknod: \1: File exists/"
 }
 
+_filter_lostfound()
+{
+	sed -e '/^lost+found$/d'
+}
+
 # make sure this script returns success
 /bin/true