generic: require journal in shutdown tests

generic: require journal in shutdown tests

Tests in shutdown group are supposed to test journal recovery after
filesystem shutdown, and the tests assume the filesystem in test has
journal support. But with the ext4 shutdown function added in
4.11-rc kernel, ext2 gains shutdown support too when driving with
ext4 driver, so generic/051 fails because fs corruption after test.

Adding _require_metadata_journaling to all generic tests in shutdown
group to ensure there's journal present.

generic/050 is skipped because it has _require_scratch_nocheck,
which indicates no fsck is done after test.

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