HADOOP-15289. FileStatus.readFields() assertion incorrect.

Contributed by Steve Loughran.

(cherry picked from commit 12ecb55ffe)

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/fs/FileStatus.java

@@ -502,7 +502,7 @@ public class FileStatus implements Writable, Comparable<Object>,
     setPath(other.getPath());
     attr = attributes(other.hasAcl(), other.isEncrypted(),
         other.isErasureCoded(), other.isSnapshotEnabled());
-    assert (isDirectory() && getSymlink() == null) || !isDirectory();
+    assert !(isDirectory() && isSymlink()) : "A directory cannot be a symlink";
   }
 
   /**