shared/032: fix fsck failure

shared/032: fix fsck failure

while running ./check tests/shared/032, it outputs something like:

FSTYP         -- btrfs
PLATFORM      -- Linux/x86_64 vm01 3.17.0-rc5+
MKFS_OPTIONS  -- /dev/sdc
MOUNT_OPTIONS -- /dev/sdc /mnt/scratch

shared/032 2s ... 2s
_check_btrfs_filesystem: filesystem on /dev/sdc is inconsistent (see /root/xfstests-dev/results//shared/032.full)
Ran: shared/032
Passed all 1 tests

This is because xfstests will run fsck after each unit test,
for tests/shared/032, we have reformated SCRATCH_DEV to other fs,
fix this problem by skipping fsck here.

Signed-off-by: Wang Shilong <wangshilong1991@gmail.com>
Reviewed-by: Eryu Guan <eguan@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>