test_extension_manager uses nonexistent function

[Juan Antonio Osorio Robles]

test_extension_manager uses the nonexistent function assert_called_once to test if a call was being issued, but this function does not exist and is improperly being ignored by the mock interface.

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/97745
Committed: https://git.openstack.org/cgit/openstack/barbican/commit/?id=e1593107f6d3b2d9a69b84731116e48a289af3be
Submitter: Jenkins
Branch: master

commit e1593107f6d3b2d9a69b84731116e48a289af3be
Author: Juan Antonio Osorio <email address hidden>
Date: Wed Jun 4 13:34:23 2014 +0300

    Replace nonexistent function in test

    test_extension_manager was trying to use assert_called_once, but this
    function is nonexistent, and was being improperly ignored by the mock
    interface. This patch fixes that by checking the call count of the
    mocked function, and checking it.

    Change-Id: Id00b4a7bb58e8ca71ca1d0878f9f2a28f1052f92
    Closes-Bug: #1326344