xfs/310: Cleanup

Cleanup couple of things that were objected to when creating test
ext4/033 out of this one.

Use _require_scratch_nocheck instead of recreating scratch fs before
exiting. Avoid needless cleanup of dmhugedev on exit - _cleanup
takes care of that. Use _scratch_unmount where possible.

Signed-off-by: Jan Kara <jack@suse.cz>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Eryu Guan <guaneryu@gmail.com>
diff --git a/tests/xfs/310 b/tests/xfs/310
index f33a15a..5c1f20c 100755
--- a/tests/xfs/310
+++ b/tests/xfs/310
@@ -35,7 +35,6 @@
 	umount $SCRATCH_MNT > /dev/null 2>&1
 	rm -rf $tmp.*
-	_scratch_mkfs >/dev/null 2>&1
 # get standard environment, filters and checks
@@ -46,7 +45,7 @@
 # real QA test starts here
 _supported_os Linux
 _supported_fs xfs
 _require_xfs_io_command "falloc"
@@ -60,7 +59,7 @@
 blksz="$(_get_block_size $SCRATCH_MNT)"
-umount $SCRATCH_MNT
 echo "Format huge device"
 nr_blks=2100000	# 2^21 plus a little more
@@ -110,7 +109,6 @@
 echo "Check and fake-repair huge filesystem again" | tee -a $seqres.full
 $XFS_REPAIR_PROG -n $DMHUGEDISK_DEV >> $seqres.full 2>&1
 echo "Done"