ensure heartbeating is setup following reconnect

Author: grs

lib/connection.js

@@ -545,7 +545,10 @@ Connection.prototype.eof = function (e) {
 };
 
 Connection.prototype._disconnected = function (error) {
-    if (this.heartbeat_out) clearTimeout(this.heartbeat_out);
+    if (this.heartbeat_out) {
+        clearTimeout(this.heartbeat_out);
+        this.heartbeat_out = undefined;
+    }
     if (this.heartbeat_in) clearTimeout(this.heartbeat_in);
     var was_closed_with_non_fatal_error = this.closed_with_non_fatal_error;
     if (this.closed_with_non_fatal_error) {