Add secret_type to Secret constructor

The secret_type attribute was recently introduced on the Barbican
server. [1]  Passing a response that includes the secret_type to the
constructor results in a TypeError

This is the kind of error that the upcoming python-barbicanclient gate
will help find.  It should be covered by an existing test in the
functional test suite.

[1] https://review.openstack.org/#/c/156385/

Change-Id: Ibcf42a79ec11e9c05121763ab18d9bc41d6f4dcf
Closes-Bug: #1427423

barbicanclient/secrets.py

@@ -80,7 +80,7 @@ class Secret(SecretFormatter):
                  bit_length=None, mode=None, payload=None,
                  payload_content_type=None, payload_content_encoding=None,
                  secret_ref=None, created=None, updated=None,
-                 content_types=None, status=None):
+                 content_types=None, status=None, secret_type=None):
         """
         Secret objects should not be instantiated directly.  You should use
         the `create` or `get` methods of the