Incorporated feedback from jackstontj
Incorporated feedback from jackstontj

- Added comment in `_remove_client_present` explaining how not
having the client in the list is possible.
- Removed unnecessary copy operations in `publish_payload`.
- Changed `return` to `break` in `_stream_read`. Note that `return`
is technically valid.
- Renamed `PubServerClient` to `Subscriber`.

saltstack/salt,saltstack/salt,saltstack/salt,saltstack/salt,saltstack/salt