Fix windows tests skipping

* add call to setUp from inherited test class

tests/lib/archive/tar.php

@@ -8,8 +8,14 @@
 
 require_once 'archive.php';
 
-if (!OC_Util::runningOnWindows()) {
 class Test_Archive_TAR extends Test_Archive {
+	public function setUp() {
+		if (OC_Util::runningOnWindows()) {
+			$this->markTestSkipped('tar archives are not supported on windows');
+		}
+		parent::setUp();
+	}
+
 	protected function getExisting() {
 		$dir = OC::$SERVERROOT . '/tests/data';
 		return new OC_Archive_TAR($dir . '/data.tar.gz');
@@ -19,4 +25,3 @@ class Test_Archive_TAR extends Test_Archive {
 		return new OC_Archive_TAR(OCP\Files::tmpFile('.tar.gz'));
 	}
 }
-}