Move IRC->AMQP message sending into AMQP process

Move IRC->AMQP message sending into AMQP process

This allows the message to be dropped if, for example, the AMQP process is
sleeping on the rate limit timer and causes a timeout instead of handling the
get_connection call.  Previously, this would crash the init process of
irc_amqp_listener, and since the gen_server timeout is only 5 seconds, the
irc_object_sup would reach its max restart intensity and exit.

As an added bonus: this is actually more reasonable message passing anyway.