Include rooms with 1 person invited

[dbkr]

If we can't find one with both people joined.

Also update function to es6 variable declarations.

[ara4n]

tests failing with

SyntaxError: src/components/views/rooms/MemberInfo.js: Unexpected token (135:59)
                invited.length === 1 &&
                userIds.indexOf(members[0].userId) !== -1 &&
                userIds.indexOf(invited[0].userId) !== -1) &&
                invitedRoomId === null
            {
                invitedRoomId = rooms[i].roomId;

otherwise lgtm

[ara4n]

lgtm