LoginStrategy.java : Fixed sonar issue

Fixed sonar issue, annotate interface with @FunctionalInterface
annotation

Issue-ID: PORTAL-374
Change-Id: I30472b6c18ef350b687d74acce4545c250462f6d
Signed-off-by: Arundathi Patil <arundpil@in.ibm.com>
diff --git a/ecomp-portal-BE-os/src/main/java/org/onap/portalapp/authentication/LoginStrategy.java b/ecomp-portal-BE-os/src/main/java/org/onap/portalapp/authentication/LoginStrategy.java
index d5eae39..dbbf1de 100644
--- a/ecomp-portal-BE-os/src/main/java/org/onap/portalapp/authentication/LoginStrategy.java
+++ b/ecomp-portal-BE-os/src/main/java/org/onap/portalapp/authentication/LoginStrategy.java
@@ -3,6 +3,8 @@
  * ONAP Portal
  * ===================================================================
  * Copyright (C) 2017 AT&T Intellectual Property. All rights reserved.
+ * 
+ * Modifications Copyright (C) 2018 IBM.
  * ===================================================================
  *
  * Unless otherwise specified, all software contained herein is licensed
@@ -40,6 +42,7 @@
 import javax.servlet.http.HttpServletRequest;
 import javax.servlet.http.HttpServletResponse;
 
+@FunctionalInterface
 public interface LoginStrategy {
 	public boolean login(HttpServletRequest request, HttpServletResponse response)  throws Exception;
 }