Allow tests to run with both provenances of mox

We currently have a requirement for mox >= 0.5.3.

Confusingly there are two flavours of "mox 0.5.3"
in the wild:

1) pypi's mox-0.5.3.tar.gz (https://pypi.python.org/pypi/mox)
2) Google's mox-0.5.3.tar.gz (https://code.google.com/p/pymox/)

These are not exactly the same; tests which can pass on (1) may
fail on (2).

Fedora packages are based on (1) while Debian/Ubuntu packages
are based on (2).

This is a known issue: https://code.google.com/p/pymox/issues/detail?id=40

When running the tests using a virtual env (1) is used, but
on Debian/Ubuntu when not running using a virtual env (2)
will be used: this leads to 3 of the 1740 tests failing.

This patch allows all 1743 tests to run whether you are running
in a virtual env or using Debian/Ubuntu/Fedora packages.

Fix for bug 1212625.

Change-Id: Ib0b11ec18aafbfb7f3d243bf149b94f93a1c13c9
Merge "Allow tests to run with both provenances of mox"