Replace Mox with Mock

According to [1] "New test cases should be implemented using Mock.
It is part of the Python standard library in Python 3 and as such
is the preferred method for OpenStack." So let's kill Mox in favor
of Mock.

[1] http://docs.openstack.org/infra/manual/developers.html#peer-review

Change-Id: I0db1cf3969a8d5ae90e1a13330799e69c7751207
17 files changed