Vault secretstore plugin doesn't support asymmetric key generation for
now, so disable the related functional tests.
With this patch, the following functional tests sould be skipped:
api.v1.functional.test_orders.OrdersTestCase.test_encryption_using_generated_key
api.v1.functional.test_rsa.RSATestCase.test_rsa_order_certificate_from_ordered_container
api.v1.functional.test_rsa.RSATestCase.test_rsa_order_certificate_from_ordered_container_with_pass
api.v1.functional.test_rsa.RSATestCase.test_rsa_order_container
api.v1.functional.test_rsa.RSATestCase.test_rsa_order_container_with_passphrase
Change-Id: If416f38cb87bdb279a05263b99b5f2af916c1229