Cleaned up PMD violations in SDN-IP

Change-Id: I325c2a451cb8ab17c00f7ceda8f1958b2aba6cfb
diff --git a/src/main/java/net/onrc/onos/apps/bgproute/Prefix.java b/src/main/java/net/onrc/onos/apps/bgproute/Prefix.java
index 74b6ad9..9ba046c 100644
--- a/src/main/java/net/onrc/onos/apps/bgproute/Prefix.java
+++ b/src/main/java/net/onrc/onos/apps/bgproute/Prefix.java
@@ -128,7 +128,7 @@
                     return result.toString();
                 }
             }
-            result.append(" ");
+            result.append(' ');
         }
         return result.substring(0, result.length() - 1);
     }