Properly unreference socket in order to avoid FIN_WAIT2

Author: bwoebi

lib/Rfc6455Endpoint.php

@@ -124,6 +124,7 @@ private function tryAppOnClose($code, $reason) {
 
     private function unloadClient() {
         $this->parser = null;
+        $this->socket = null;
         if ($this->readWatcher) {
             \Amp\cancel($this->readWatcher);
         }
@@ -698,4 +699,4 @@ static public function parser(callable $emitCallback, array $options = []) {
             yield 0;
         }
     }
-}
+}