Handle distribute -> setuptools migration.

Running just 'pip install -U distribute' can leave setuptools in a
half migrated state on Fedora/RHEL/CentOS.  Following it up with 'pip
install -U setuptools' corrects the problem and leaves you with
distribute 0.7.3 and the latest setuptools.

Change-Id: I3652e84fcfdc39065b6b86fc85b6b6602601d7e9
Merge "Handle distribute -> setuptools migration."