message: Reorder checks in has_message_access.
message: Reorder checks in has_message_access.

This refactor makes this function easier to read and understand.

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