Enable checkstyle trailing spaces rule

Enable the checkstyle rule that detects unneeded trailing spaces
and fix the violations of the rule.

Change-Id: I65567c87142c5a257f0230a55bc4376e770d416f
diff --git a/src/main/java/net/onrc/onos/apps/bgproute/RestClient.java b/src/main/java/net/onrc/onos/apps/bgproute/RestClient.java
index 3164945..e0976cc 100644
--- a/src/main/java/net/onrc/onos/apps/bgproute/RestClient.java
+++ b/src/main/java/net/onrc/onos/apps/bgproute/RestClient.java
@@ -17,7 +17,7 @@
     private RestClient() {
         // Private constructor to prevent instantiation
     }
-    
+
     public static String get(String str) {
         StringBuilder response = new StringBuilder();