fix for service not found error

Change-Id: I92091b5932e2ecefb074861085015393b8d1b61d
(cherry picked from commit cab2869c3115bcbe11f310c8b7dfdf44c76c6e5b)
diff --git a/web/api/src/main/java/org/onosproject/rest/resources/AuditFilter.java b/web/api/src/main/java/org/onosproject/rest/resources/AuditFilter.java
index 81c4f42..40749f3 100644
--- a/web/api/src/main/java/org/onosproject/rest/resources/AuditFilter.java
+++ b/web/api/src/main/java/org/onosproject/rest/resources/AuditFilter.java
@@ -85,7 +85,12 @@
     }
 
     private AuditService auditService() {
-        AuditService auditService = disableForTests ? null : services.get(AuditService.class);
+        AuditService auditService = null;
+        try {
+            auditService = disableForTests ? null : services.get(AuditService.class);
+        } catch (org.onlab.osgi.ServiceNotFoundException e) {
+            return null;
+        }
         return auditService != null && auditService.isAuditing() ? auditService : null;
     }
 }