dos: Overwrite of the connection stats in the heartbeat

Commit 94b56eaa merged yesterday had an issue I found out later that night.

The commit added the rejected connect we would do to the heartbeat but the code overwrites the existing stats of how many connections were closed from the concurrent detection. See, conn_msg is overwritten.

     tor_asprintf(&conn_msg,
                  " %" PRIu64 " connections closed.",
                  conn_num_addr_rejected);
+    tor_asprintf(&conn_msg,
+                 " %" PRIu64 " connect() connections closed.",
+                 conn_num_addr_connect_rejected);