Overlay tuning and logging improvements:

Adjust overlay tuning to reflect measured behavior of the
network under increased load.

Improve logging of peer sendq size and disconnect reasons.

src/ripple/overlay/impl/PeerImp.cpp

@@ -210,6 +210,12 @@ PeerImp::send (Message::pointer const& m)
         // a small senq periodically
         large_sendq_ = 0;
     }
+    else if ((sendq_size % Tuning::sendQueueLogFreq) == 0)
+    {
+        JLOG (journal_.debug()) <<
+            (name_.empty() ? remote_address_.to_string() : name_) <<
+                " sendq: " << sendq_size;
+    }
 
     send_queue_.push(m);
 
@@ -442,7 +448,9 @@ PeerImp::fail(std::string const& reason)
                 shared_from_this(), reason));
     if (socket_.is_open())
     {
-        JLOG (journal_.debug()) << reason;
+        JLOG (journal_.warn()) <<
+            (name_.empty() ? remote_address_.to_string() : name_) <<
+                " failed: " << reason;
     }
     close();
 }