Since route_msg expects msg.prefix to be present, every plugin that
calls route_msg when no prefix is specified in the message (e.g. with
PING messages) would cause a crash of the process.
Now, it just calls a no-op function, since all behavior covered by
route_message requires information in the prefix at some point.
Signed-off-by: Alek Ratzloff <alekratz@gmail.com>
