Fix issues with grizzly

- Install a known working recent version of pip (cherry-picked from
  62d1d698a0c1459)
- Don't install boto from pip let use the default from ubuntu or the
  euac2ools will fails.
- Don't install netaddr from the packages let the pip do its job without
  being confused.
- Skip excercises that fails on grizzly.

Change-Id: I27df3787b5b90621ea66e4cc9763365b4579e3ca