Investigate possible opencryptoki regression w.r.t. stream cancellations

[MatthiasValvekens]

Some time between April and now opencryptoki tests started failing with this error:

self = <tests.test_rsa.RSATests testMethod=test_verify_stream_interrupt_releases_operation>

    @requires(Mechanism.SHA512_RSA_PKCS)
    def test_verify_stream_interrupt_releases_operation(self):
        data = (
            b"I" * 16,
            b"N" * 16,
            b"P" * 16,
            b"U" * 16,
            b"T" * 10,
        )
    
        def _data_with_error():
            yield data[0]
            yield data[1]
            yield data[2]
            raise ValueError
    
        signature = self.private.sign(data)
    
        def attempt_verify():
            self.public.verify(_data_with_error(), signature)
    
        self.assertRaises(ValueError, attempt_verify)
        # ...try again
>       self.assertTrue(self.public.verify(data, signature))
                        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

Our code didn't change, so this is probably an upstream regression. To be investigated.