node test: Add message for unread/mentions test.
node test: Add message for unread/mentions test.

Add the "control" case here of a message that is
already read.

brainwane/zulip,zulip/zulip,rht/zulip,hackerkid/zulip,synicalsyntax/zulip,timabbott/zulip,synicalsyntax/zulip,rht/zulip,brainwane/zulip,timabbott/zulip,showell/zulip,hackerkid/zulip,kou/zulip,kou/zulip,shubhamdhama/zulip,andersk/zulip,punchagan/zulip,zulip/zulip,synicalsyntax/zulip,punchagan/zulip,eeshangarg/zulip,synicalsyntax/zulip,timabbott/zulip,zulip/zulip,shubhamdhama/zulip,synicalsyntax/zulip,hackerkid/zulip,kou/zulip,eeshangarg/zulip,showell/zulip,zulip/zulip,brainwane/zulip,punchagan/zulip,andersk/zulip,rht/zulip,punchagan/zulip,timabbott/zulip,andersk/zulip,andersk/zulip,eeshangarg/zulip,eeshangarg/zulip,shubhamdhama/zulip,brainwane/zulip,showell/zulip,shubhamdhama/zulip,andersk/zulip,rht/zulip,punchagan/zulip,brainwane/zulip,hackerkid/zulip,timabbott/zulip,timabbott/zulip,hackerkid/zulip,eeshangarg/zulip,showell/zulip,zulip/zulip,punchagan/zulip,shubhamdhama/zulip,eeshangarg/zulip,eeshangarg/zulip,hackerkid/zulip,kou/zulip,brainwane/zulip,shubhamdhama/zulip,kou/zulip,synicalsyntax/zulip,hackerkid/zulip,kou/zulip,timabbott/zulip,andersk/zulip,andersk/zulip,punchagan/zulip,kou/zulip,brainwane/zulip,showell/zulip,rht/zulip,zulip/zulip,showell/zulip,showell/zulip,synicalsyntax/zulip,zulip/zulip,shubhamdhama/zulip,rht/zulip,rht/zulip