fixed unittests

Author: oliverlorenz

src/packet/ControlPacket.php

@@ -161,7 +161,7 @@ public function get()
      * @param $byte1
      * @return $byte1 unmodified
      */
-    protected function addReservedBitsToFixedHeaderControlPacketType($byte1)
+    protected static function addReservedBitsToFixedHeaderControlPacketType($byte1)
     {
         return $byte1;
     }

src/packet/Subscribe.php

@@ -20,7 +20,7 @@ public static function getControlPacketType()
         return ControlPacketType::SUBSCRIBE;
     }
 
-    protected function addReservedBitsToFixedHeaderControlPacketType($byte1)
+    protected static function addReservedBitsToFixedHeaderControlPacketType($byte1)
     {
         return $byte1 + 2;
     }