.travis.yml: Update install commands

Signed-off-by: Lucas Meneghel Rodrigues <lmr@redhat.com>
.travis.yml: Use system site packages

Signed-off-by: Lucas Meneghel Rodrigues <lmr@redhat.com>
virttest: Fix NumaNode unittesting

The NumaNode unittest was directly accessing system
files, making it fail on Travis CI jobs. Let's fix
that by adding some extra params to the NumaNode API,
that allow to replace the system locations and execute
our tests.

Signed-off-by: Lucas Meneghel Rodrigues <lmr@redhat.com>
Merge pull request #1599 from autotest/travis-fixes

.travis.yml: Update install commands