ci/create-docker-image: Fix GOPATH inside the build container
ci/create-docker-image: Fix GOPATH inside the build container

When running the skydive build (compile) inside the build container:
Instead of using $GOPATH from the host (which is something like
/home/user/go) as-is inside the builder conatiner, use the proper
$GOPATH directory which is /root/go.

lebauce/skydive,skydive-project/skydive,skydive-project/skydive,lebauce/skydive,lebauce/skydive,skydive-project/skydive,skydive-project/skydive,skydive-project/skydive,lebauce/skydive,lebauce/skydive,lebauce/skydive,skydive-project/skydive,skydive-project/skydive,lebauce/skydive,lebauce/skydive