refactor: Only return sub from access_stream_common.
refactor: Only return sub from access_stream_common.

Let the callers access stream.recipient as needed.
It costs the same, and some of the callers can
actually stop caring about the actual Recipient
object.

andersk/zulip,hackerkid/zulip,showell/zulip,showell/zulip,andersk/zulip,andersk/zulip,eeshangarg/zulip,punchagan/zulip,showell/zulip,punchagan/zulip,andersk/zulip,eeshangarg/zulip,kou/zulip,eeshangarg/zulip,eeshangarg/zulip,punchagan/zulip,hackerkid/zulip,showell/zulip,zulip/zulip,kou/zulip,showell/zulip,zulip/zulip,zulip/zulip,rht/zulip,zulip/zulip,rht/zulip,rht/zulip,punchagan/zulip,andersk/zulip,rht/zulip,eeshangarg/zulip,kou/zulip,eeshangarg/zulip,kou/zulip,andersk/zulip,punchagan/zulip,zulip/zulip,andersk/zulip,showell/zulip,hackerkid/zulip,zulip/zulip,hackerkid/zulip,punchagan/zulip,kou/zulip,eeshangarg/zulip,rht/zulip,hackerkid/zulip,hackerkid/zulip,rht/zulip,rht/zulip,zulip/zulip,punchagan/zulip,showell/zulip,kou/zulip,hackerkid/zulip,kou/zulip