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/FilesystemValueCheckerTest.java b/src/test/java/com/google/devtools/build/lib/skyframe/FilesystemValueCheckerTest.java
index d1d2018..69a267b 100644
--- a/src/test/java/com/google/devtools/build/lib/skyframe/FilesystemValueCheckerTest.java
+++ b/src/test/java/com/google/devtools/build/lib/skyframe/FilesystemValueCheckerTest.java
@@ -86,7 +86,7 @@
   private TimestampGranularityMonitor tsgm;
 
   @Before
-  public void setUp() throws Exception {
+  public final void setUp() throws Exception  {
     ImmutableMap.Builder<SkyFunctionName, SkyFunction> skyFunctions = ImmutableMap.builder();
 
     fs = new MockFileSystem();