rabbit_connection_tracking_handler: handle more errors when registering a connection

Due to #1869, a connection can be accepted before connection tracking
tables were initialized/synced from a peer. The handler should log
a warning and not terminate, even if it would be restarted, to reduce
log noise and scare fewer operators for no real reason:
the condition is transient and should not normally last for more than
a few tenths of a second.

Author: michaelklishin

src/rabbit_connection_tracking_handler.erl

@@ -58,8 +58,14 @@ handle_event(#event{type = connection_created, props = Details}, State) ->
                     rabbit_connection_tracking:tracked_connection_from_connection_created(Details)
                 )
             catch
-                error:{no_exists,_} ->
-                    rabbit_log_connection:error("Failed to track new connection, it terminated prematurely"),
+                error:{no_exists, _} ->
+                    Msg = "Could not register connection ~p for tracking, "
+                          "its table is not ready yet or the connection terminated prematurely",
+                    rabbit_log_connection:warning(Msg, [pget(pid, Details)]),
+                    ok;
+                error:Err ->
+                    Msg = "Could not register connection ~p for tracking: ~p",
+                    rabbit_log_connection:warning(Msg, [pget(pid, Details), Err]),
                     ok
             end;
       _OtherNode ->