Migrated tests in devtools/build/lib/skyframe to JUnit 4.

--
MOS_MIGRATED_REVID=109286530
diff --git a/src/test/java/com/google/devtools/build/lib/skyframe/DiffAwarenessManagerTest.java b/src/test/java/com/google/devtools/build/lib/skyframe/DiffAwarenessManagerTest.java
index 1ade3d4..90d53fb 100644
--- a/src/test/java/com/google/devtools/build/lib/skyframe/DiffAwarenessManagerTest.java
+++ b/src/test/java/com/google/devtools/build/lib/skyframe/DiffAwarenessManagerTest.java
@@ -51,10 +51,13 @@
   protected EventCollectionApparatus events;
 
   @Before
-  public void setUp() throws Exception {
-    
+  public final void createFileSystem() throws Exception  {
     fs = new InMemoryFileSystem();
     root = fs.getRootDirectory();
+  }
+
+  @Before
+  public final void initializeEventCollectionApparatus() {
     events = new EventCollectionApparatus();
     events.setFailFast(false);
   }