HDFS-14975. Add CR for SetECPolicyCommand usage. Contributed by Fei Hui.

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/tools/ECAdmin.java

@@ -330,7 +330,7 @@ public class ECAdmin extends Configured implements Tool {
           "Set the erasure coding policy for a file/directory.\n\n" +
           listing.toString() + "\n" +
           "-replicate and -policy are optional arguments. They cannot been " +
-          "used at the same time";
+          "used at the same time.\n";
     }
 
     @Override