ext4/053: fix the rejected mount option testing

ext4/053: fix the rejected mount option testing

'not_mnt OPTIONS' seems to have been intended to test that the
filesystem cannot be mounted at all with the given OPTIONS, meaning that
the mount fails as opposed to the options being ignored.  However, this
doesn't actually work, as shown by the fact that the test case 'not_mnt
test_dummy_encryption=v3' is passing in the !CONFIG_FS_ENCRYPTION case.
Actually ext4 ignores this mount option when !CONFIG_FS_ENCRYPTION.
(The ext4 behavior might be changed, but that is besides the point.)

The problem is that the do_mnt() helper function is being misused in a
context where a mount failure is expected, and it does some additional
remount tests that don't make sense in that context.  So if the mount
unexpectedly succeeds, then one of these later tests can still "fail",
causing the unexpected success to be shadowed by a later failure, which
causes the overall test case to pass since it expects a failure.

Fix this by reworking not_mnt() and not_remount_noumount() to use
simple_mount() in cases where they are expecting a failure.  Also fix
up some of the naming and calling conventions to be less confusing.
Finally, make sure to test that remounting fails too, not just mounting.

Signed-off-by: Eric Biggers <ebiggers@google.com>
Reviewed-by: Lukas Czerner <lczerner@redhat.com>
Signed-off-by: Zorro Lang <zlang@kernel.org>