PackInserterTest#newLargeBlob: Factor Random instance out to class member

Instead of instantiating a new Random on each invocation of newLargeBlob,
create it once and reuse it.

This fixes a warning raised by Spotbugs about the Random object being
created and only used once.

Change-Id: I5b8e6ccbbc92641811537808aed9eae2034c1133
Signed-off-by: David Pursehouse <david.pursehouse@gmail.com>

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

@@ -95,6 +95,8 @@ import org.junit.Test;
 public class PackInserterTest extends RepositoryTestCase {
 	private WindowCacheConfig origWindowCacheConfig;
 
+	private static final Random random = new Random(0);
+
 	@Before
 	public void setWindowCacheConfig() {
 		origWindowCacheConfig = new WindowCacheConfig();
@@ -518,7 +520,7 @@ public class PackInserterTest extends RepositoryTestCase {
 
 	private static byte[] newLargeBlob() {
 		byte[] blob = new byte[10240];
-		new Random(0).nextBytes(blob);
+		random.nextBytes(blob);
 		return blob;
 	}