generic/397: remove workarounds for wrong error codes

generic/397: remove workarounds for wrong error codes

generic/397 contains workarounds to allow for kernel bugs where trying
to open or create files in an encrypted directory without the encryption
key failed with ENOENT, EACCES, or EPERM instead of the expected ENOKEY.

However, all these bugs have been fixed.  ext4 and f2fs were fixed years
ago by commit 54475f531bb8 ("fscrypt: use ENOKEY when file cannot be
created w/o key").  ubifs was fixed by commit b01531db6cec ("fscrypt:
fix race where ->lookup() marks plaintext dentry as ciphertext").

It's been long enough, so update the test to expect the correct behavior
only, so we don't accidentally reintroduce the wrong behavior.

Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Eryu Guan <guaneryu@gmail.com>