Unread private topic indicator doesn't always clear

[jaysylvester]

Occasionally, the header cache will clear and reload before the private topic view time update occurs, keeping the icon in its unread state.

[jaysylvester]

Moving viewTimeUpdate() into listen() now ensures the unread marker is updated before the header is rendered/cached in all cases. Should fix this issue. Side benefit is that the unread marker is now cleared during the same topic request, whereas previously it would remain unread because the header was rendered before viewTimeUpdate() executed.