[FAB-3198] gossip: Un-necessary WARN log at shutdown

The gossip comm layer exposes a subscription-like API and
returns a dedicated channel to the caller.

Since it is convenient to iterate over a channel until it's closed,
or to understand that a channel has been closed when nil is returned
from select - it was implemented that at the comm layer shutdown -
the subscriptions channels are closed.

This might have caused a "send to closed channel" error-
and so- the implementation has a defer statement with recover()
that recovers from that.

However- it also logs a WARN message un-necessarily because that's not
something that shouldn't have happened.

Change-Id: I50d03eb8482e115782b3e4090330f72720883028
Signed-off-by: Yacov Manevich <yacovm@il.ibm.com>

gossip/comm/comm_impl.go

@@ -347,7 +347,6 @@ func (c *commImpl) Accept(acceptor common.MessageAcceptor) <-chan proto.Received
 	go func() {
 		defer c.logger.Debug("Exiting Accept() loop")
 		defer func() {
-			c.logger.Warning("Recovered")
 			recover()
 		}()