shared/272: don't use data journaling with DAX

shared/272 fails with kernels v4.15-rc1 and beyond when you are
mounted with DAX:

shared/272	 [failed, exit status 1] - output mismatch (see
/root/project/xfstests/results//shared/272.out.bad)
    --- tests/shared/272.out	2015-12-05 13:12:17.038257578 -0700
    +++ /root/project/xfstests/results//shared/272.out.bad	2018-01-17
    15:37:18.581631116 -0700
    @@ -1,3 +1,3 @@
     QA output created by 272
     Switch data journalling mode. Silence is golden.
    -Check filesystem
    +/usr/bin/chattr: Device or resource busy while setting flags on
    /mnt/xfstests_scratch/file.1
    ...
    (Run 'diff -u tests/shared/272.out
    /root/project/xfstests/results//shared/272.out.bad'  to see the entire
    diff)

This is expected.  The following kernel commit:

commit e9072d859df3 ("ext4: prevent data corruption with journaling + DAX")

makes "chattr +j", which is attempting to turn on data journaling,
return -EBUSY if the ext4 DAX mount option is in use.  This was done
to prevent the data corruption shown in xfstest ext4/030, added by
this xfstests commit:

commit 750a24e99e ("ext4: test for DAX + journaling corruption")

So, just skip shared/272 if the DAX mount option is in use.

Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Reviewed-by: Eryu Guan <eguan@redhat.com>
Signed-off-by: Eryu Guan <eguan@redhat.com>

tests/shared/272

@@ -83,6 +83,7 @@ chattr_opt: $chattr_opt" >>$seqres.full
 _supported_fs ext3 ext4
 _supported_os Linux
 _require_scratch
+_exclude_scratch_mount_option dax
 
 rm -f $seqres.full
 _scratch_mkfs_sized $((64 * 1024 * 1024)) >> $seqres.full 2>&1