CheckoutCommandTest: Fix name of created temp file

Change-Id: I29048f83aee3848679bbc6ded09dd3dd4a2ea35b
Signed-off-by: David Pursehouse <david.pursehouse@gmail.com>

org.eclipse.jgit.test/tst/org/eclipse/jgit/api/CheckoutCommandTest.java

@@ -824,7 +824,7 @@ public class CheckoutCommandTest extends RepositoryTestCase {
 	}
 
 	private File writeTempFile(String body) throws IOException {
-		File f = File.createTempFile("AddCommandTest_", "");
+		File f = File.createTempFile("CheckoutCommandTest_", "");
 		JGitTestUtil.write(f, body);
 		return f;
 	}