Fix AsyncBusTests

Signed-off-by: Roeland Jago Douma <roeland@famdouma.nl>

tests/lib/Command/AsyncBusTest.php

 
 	public function testClosureSelf() {
 		$this->getBus()->push(function () {
-			self::$lastCommand = 'closure-self';
+			AsyncBusTest::$lastCommand = 'closure-self';
 		});
 		$this->runJobs();
 		$this->assertEquals('closure-self', self::$lastCommand);
 	public function testClosureBind() {
 		$state = 'bar';
 		$this->getBus()->push(function () use ($state) {
-			self::$lastCommand = 'closure-' . $state;
+			AsyncBusTest::$lastCommand = 'closure-' . $state;
 		});
 		$this->runJobs();
 		$this->assertEquals('closure-bar', self::$lastCommand);