Fix bug in SkyQuery's 'rbuildfiles' implementation where we were incorrectly using FileValue, rather than FileStateValue, nodes as the roots of the rdep traversal.

This is incorrect e.g. when a .bzl file is a target of a symlink that is load'd from a BUILD file.

RELNOTES: None
PiperOrigin-RevId: 177018264
diff --git a/src/main/java/com/google/devtools/build/lib/query2/ParallelSkyQueryUtils.java b/src/main/java/com/google/devtools/build/lib/query2/ParallelSkyQueryUtils.java
index 1948cb0..57485d9 100644
--- a/src/main/java/com/google/devtools/build/lib/query2/ParallelSkyQueryUtils.java
+++ b/src/main/java/com/google/devtools/build/lib/query2/ParallelSkyQueryUtils.java
@@ -87,7 +87,7 @@
     Uniquifier<SkyKey> keyUniquifier = env.createSkyKeyUniquifier();
     RBuildFilesVisitor visitor =
         new RBuildFilesVisitor(env, keyUniquifier, callback);
-    visitor.visitAndWaitForCompletion(env.getSkyKeysForFileFragments(fileIdentifiers));
+    visitor.visitAndWaitForCompletion(env.getFileStateKeysForFileFragments(fileIdentifiers));
   }
 
   /** A helper class that computes 'rbuildfiles(<blah>)' via BFS. */