travis: upgrade ubuntu release and add arm64 testing
travis: upgrade ubuntu release and add arm64 testing

Signed-off-by: Matias Elo <62402263e8617147f0e4dd5b7f6f8ec67f2b3d2c@nokia.com>

OpenFastPath/ofp,OpenFastPath/ofp,OpenFastPath/ofp,OpenFastPath/ofp