[PATCH v2] xfstests: fix to make tests/btrfs/013 work using all version btrfs progs

[ZhangZhen <zhenzhang.zhang@xxxxxxxxxx>]

The test 013 couldn't work using some old version btrfs progs
e.g.(btrfs progs v0.19 openSUSE 12.3)because here lacked "start".
This patch fix it.

Signed-off-by: Zhang Zhen <zhenzhang.zhang@xxxxxxxxxx>
---
 tests/btrfs/013 | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tests/btrfs/013 b/tests/btrfs/013
index 7620fcc..fb81663 100644
--- a/tests/btrfs/013
+++ b/tests/btrfs/013
@@ -72,7 +72,7 @@ _check_csum_error()
 }
 $XFS_IO_PROG -f -c "falloc 0 1M" -c "pwrite 16k 8k" -c "fsync" \
        $SCRATCH_MNT/foo > $seqres.full 2>&1
-$BTRFS_UTIL_PROG filesystem balance $SCRATCH_MNT >> $seqres.full 2>&1 || \
+$BTRFS_UTIL_PROG filesystem balance start $SCRATCH_MNT >> $seqres.full 2>&1 || 
\
        _fail "balance failed"
 _scratch_unmount
 _scratch_mount