bug 321 - Stop reconnecting to providers

bug 321 - Stop reconnecting to providers

Event origins that are not set origins will have
multiple  li_origin/li_receiver pairs in sl_listen
we listen for events from these origins from multiple
sources.   This means a node such as node 2 might
receive an event from ev_origin=1 via event provider 1
then receive the next event with ev_origin=1 from
event provider 2.  Slon keeps connecting and
disconnecting from these providers.

Instead keep of dropping the connections to
event providers we keep them around unless
a reconfiguration has taken place.  This lets
us use the connection for the event_provider
we received the event from.