Drop workaround for pip < 1.4

Now that we are on pip 1.5.6 lets drop the workaround to make pip 1.4
work. As this is a development/testing tool requiring a newer pip
shouldn't be an issue. Also stack.sh installs pip by default.

Work around introduced in https://github.com/pypa/pip/issues/709

Change-Id: I0e7aad1d21f4fce4c020ce36685bb56893c66bdc
Merge "Drop workaround for pip < 1.4"