Support --port command line option for mo script

[jyemin]

I've found that I sometimes need to run two copies of the mongo-orchestration server, and of course they can't both run on 8889. But the mo script hardcodes 8889. A command line option corresponding to the one on mongo-orchestration would be useful

[ShaneHarvey]

Why do you need to run two copies? A single MO server can handle multiple requests.