ConcurrentRepackTest: Don't use deprecated WindowCache.reconfigure

Replace with calls to WindowCacheConfig.install() as mentioned in
WindowCache.reconfigure's deprecation notice.

Change-Id: Ifdb33501a2209239029c815b1e4e844ea5b56075
Signed-off-by: David Pursehouse <david.pursehouse@sonymobile.com>

org.eclipse.jgit.test/tst/org/eclipse/jgit/internal/storage/file/ConcurrentRepackTest.java

@@ -81,15 +81,14 @@ public class ConcurrentRepackTest extends RepositoryTestCase {
 	public void setUp() throws Exception {
 		WindowCacheConfig windowCacheConfig = new WindowCacheConfig();
 		windowCacheConfig.setPackedGitOpenFiles(1);
-		WindowCache.reconfigure(windowCacheConfig);
+		windowCacheConfig.install();
 		super.setUp();
 	}
 
 	@After
 	public void tearDown() throws Exception {
 		super.tearDown();
-		WindowCacheConfig windowCacheConfig = new WindowCacheConfig();
-		WindowCache.reconfigure(windowCacheConfig);
+		new WindowCacheConfig().install();
 	}
 
 	@Test
@@ -206,7 +205,7 @@ public class ConcurrentRepackTest extends RepositoryTestCase {
 	private static void whackCache() {
 		final WindowCacheConfig config = new WindowCacheConfig();
 		config.setPackedGitOpenFiles(1);
-		WindowCache.reconfigure(config);
+		config.install();
 	}
 
 	private RevObject parse(final AnyObjectId id)