generic/053: do not unmount before calling _check_scratch_fs()

generic/053: do not unmount before calling _check_scratch_fs()

Fix generic/053 so it works on tmpfs by relying on _check_scratch_fs
to unmount before checking the file system and remounting it
afterwards.  Many other tests rely on this, and since tmpfs does not
have a file system consistency checker, this allows the test to
succeed because the files don't disappear when the tmpfs file system
is unmounted.

Signed-off-by: Junho Ryu <jayr@google.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>