travis: update go versions
travis: update go versions

Signed-off-by: Davor Kapsa <a0cec5bf91880c0c983a22e2285be007b4e1f52a@gmail.com>

liangchenye/ocitools,opencontainers/ocitools,opencontainers/ocitools,liangchenye/ocitools,opencontainers/runtime-tools,wking/ocitools-v2,wking/ocitools-v2,opencontainers/runtime-tools