travis: use the old version of docker (1.8.3)
travis: use the old version of docker (1.8.3)

Seems that the latest often fails for some reasons.

Signed-off-by: FUJITA Tomonori <93dac1fe9c4b2a3957982200319981492ad4976e@lab.ntt.co.jp>

osrg/gobgp,a16/gobgp,a16/gobgp,j-kato/gobgp,osrg/gobgp,fujita/gobgp,a16/gobgp,tamihiro/gobgp,fujita/gobgp,tamihiro/gobgp,a16/gobgp,a16/gobgp,a16/gobgp,tamihiro/gobgp,osrg/gobgp,j-kato/gobgp,ishidawataru/gobgp,tamihiro/gobgp,Dipsingh/gobgp,osrg/gobgp,ishidawataru/gobgp,fujita/gobgp,Dipsingh/gobgp,j-kato/gobgp,a16/gobgp,Dipsingh/gobgp,ishidawataru/gobgp,fujita/gobgp