Improve coverage for Intents REST API test

Also, added @Provider annotation to all exception mappers so
the Jersey unit test framework will apply them during
testing.

Change-Id: Ifd9237de2e159cd97b64dcb9bde4a66f14bd0dfc
diff --git a/web/api/src/main/java/org/onosproject/rest/exceptions/ServerErrorMapper.java b/web/api/src/main/java/org/onosproject/rest/exceptions/ServerErrorMapper.java
index 4904c85..5a9050d 100644
--- a/web/api/src/main/java/org/onosproject/rest/exceptions/ServerErrorMapper.java
+++ b/web/api/src/main/java/org/onosproject/rest/exceptions/ServerErrorMapper.java
@@ -16,10 +16,12 @@
 package org.onosproject.rest.exceptions;
 
 import javax.ws.rs.core.Response;
+import javax.ws.rs.ext.Provider;
 
 /**
  * Mapper for service not found exceptions to the INTERNAL_SERVER_ERROR response code.
  */
+@Provider
 public class ServerErrorMapper extends AbstractMapper<RuntimeException> {
     @Override
     protected Response.Status responseStatus() {