Refactor a test method including 7 test cases
Refactor a test method including 7 test cases

The test_swap_volume_volume_api_usage method
in test_compute_api.py has 7 test cases (1 normal, 6 errors).
So devide it to the following 7 test methods.

* test_swap_volume_volume_api_usage
* test_swap_volume_with_invalid_server_state
* test_swap_volume_with_old_volume_not_attached
* test_swap_volume_with_another_server_volume
* test_swap_volume_with_new_volume_attached
* test_swap_volume_with_smaller_new_volume
* test_swap_volume_with_swap_volume_error

And replace mox with mock.

Change-Id: I1ac25de5698303488a82071deed884b443951dc0

gooddata/openstack-nova,rahulunair/nova,gooddata/openstack-nova,rahulunair/nova,mikalstill/nova,openstack/nova,rahulunair/nova,mahak/nova,mikalstill/nova,phenoxim/nova,mahak/nova,klmitch/nova,klmitch/nova,jianghuaw/nova,Juniper/nova,vmturbo/nova,gooddata/openstack-nova,jianghuaw/nova,vmturbo/nova,openstack/nova,openstack/nova,Juniper/nova,Juniper/nova,jianghuaw/nova,gooddata/openstack-nova,klmitch/nova,vmturbo/nova,vmturbo/nova,Juniper/nova,mahak/nova,klmitch/nova,mikalstill/nova,jianghuaw/nova,phenoxim/nova