Un-ignored existing CLI tests which run just fine on Java 7+

Change-Id: I5ef334a49fb2d88d5e856b443687f3dcb126a77a
Signed-off-by: Andrey Loskutov <loskutov@gmx.de>

org.eclipse.jgit.pgm.test/tst/org/eclipse/jgit/pgm/AddTest.java

 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertNotNull;
 
-import java.lang.Exception;
-import java.lang.String;
-
 import org.eclipse.jgit.api.Git;
 import org.eclipse.jgit.dircache.DirCache;
 import org.eclipse.jgit.lib.CLIRepositoryTestCase;
 import org.junit.Before;
-import org.junit.Ignore;
 import org.junit.Test;
 
 public class AddTest extends CLIRepositoryTestCase {
 		git = new Git(db);
 	}
 
-	@Ignore("args4j exit()s on error instead of throwing, JVM goes down")
 	@Test
 	public void testAddNothing() throws Exception {
 		assertEquals("fatal: Argument \"filepattern\" is required", //
 				execute("git add")[0]);
 	}
 
-	@Ignore("args4j exit()s for --help, too")
 	@Test
 	public void testAddUsage() throws Exception {
 		execute("git add --help");

org.eclipse.jgit.pgm.test/tst/org/eclipse/jgit/pgm/ArchiveTest.java

 import java.io.File;
 import java.io.FileInputStream;
 import java.io.FileOutputStream;
-import java.io.InputStreamReader;
 import java.io.IOException;
+import java.io.InputStreamReader;
 import java.io.OutputStream;
-import java.lang.Object;
-import java.lang.String;
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.List;
 import java.util.concurrent.Callable;
-import java.util.concurrent.Executors;
 import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
 import java.util.concurrent.Future;
 import java.util.zip.ZipEntry;
 import java.util.zip.ZipInputStream;
 import org.eclipse.jgit.dircache.DirCache;
 import org.eclipse.jgit.lib.CLIRepositoryTestCase;
 import org.eclipse.jgit.lib.FileMode;
-import org.eclipse.jgit.pgm.CLIGitCommand;
 import org.junit.Before;
-import org.junit.Ignore;
 import org.junit.Test;
 
 public class ArchiveTest extends CLIRepositoryTestCase {
 		emptyTree = db.resolve("HEAD^{tree}").abbreviate(12).name();
 	}
 
-	@Ignore("Some versions of java.util.zip refuse to write an empty ZIP")
 	@Test
 	public void testEmptyArchive() throws Exception {
 		byte[] result = CLIGitCommand.rawExecute(