update service_shard_update to deploy on environment

[panbenson]

follow up for #3994

we should allow for deploys for certain environments, especially when using --iam-role because roles are often environment specific.
for backwards compatibility, this deploys to all environments when --environment is not passed in as an option.

[nemacysts]

the deploy_environments could probably be simplified a bit, but i won't nitpick too much since this script it owned by your team :p