bind/java/SeqTest: call Go.init from the test case constructor.

Go.init must be called once and from the main thread.
setUp is called from a non-main thread and once per each test.

Change-Id: I848a1461793463785b38141e077da5bf5e53cb4c
Reviewed-on: https://go-review.googlesource.com/6832
Reviewed-by: David Crawshaw <crawshaw@golang.org>

bind/java/SeqTest.java

@@ -9,8 +9,7 @@ import java.util.Random;
 import go.testpkg.Testpkg;
 
 public class SeqTest extends AndroidTestCase {
-  protected void setUp() throws Exception {
-    super.setUp();
+  public SeqTest() {
     Go.init(this.getContext());
   }