travis: Add 1.9 (beta) builds
travis: Add 1.9 (beta) builds

This change enables support for building with go 1.9beta2. For now this
is marked as an allowable failure and will not prevent a PR from being
merged.

Signed-off-by: Rob Bradford <c49e1dc14cd52e2644816db47123896e0ac79025@intel.com>

rbradford/ciao,kaccardi/ciao,ciao-project/ciao,kaccardi/ciao,rbradford/ciao,mcastelino/ciao,tpepper/ciao,mcastelino/ciao,01org/ciao,ciao-project/ciao,markdryan/ciao,tpepper/ciao,01org/ciao,mcastelino/ciao,tpepper/ciao,markdryan/ciao