telepathyClient: Update notification time from message

telepathyClient: Update notification time from message

As the telepathy integration picks up existing channels on startup,
ChatNotifications are another case where the real time the message
was received may be before the time it is picked up by the shell.
While this is less of an annoyance than restored GNotifications, as
it generally only affects restarts from the run dialog, it's an
easy fix now ...

https://bugzilla.gnome.org/show_bug.cgi?id=775799