write need bytes object on python 3 (ansible#35143)

Otherwise, it fail with:

    Traceback (most recent call last):
      File \"/tmp/ansible_c1zmq3i9/ansible_module_openssl_certificate.py\", line 808, in <module>
        main()
      File \"/tmp/ansible_c1zmq3i9/ansible_module_openssl_certificate.py\", line 787, in main
        certificate.generate(module)
      File \"/tmp/ansible_c1zmq3i9/ansible_module_openssl_certificate.py\", line 692, in generate
        certfile.write(str(crt))
    TypeError: a bytes-like object is required, not 'str'

lib/ansible/modules/crypto/openssl_certificate.py

@@ -757,7 +757,7 @@ def generate(self, module):
                                                             self.challenge_path),
                                          check_rc=True)[1]
                 with open(self.path, 'wb') as certfile:
-                    certfile.write(str(crt))
+                    certfile.write(to_bytes(crt))
             except OSError as exc:
                 raise CertificateError(exc)