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/BadRequestMapper.java b/web/api/src/main/java/org/onosproject/rest/exceptions/BadRequestMapper.java
index fcef3b1..89b1368 100644
--- a/web/api/src/main/java/org/onosproject/rest/exceptions/BadRequestMapper.java
+++ b/web/api/src/main/java/org/onosproject/rest/exceptions/BadRequestMapper.java
@@ -16,11 +16,14 @@
 package org.onosproject.rest.exceptions;
 
 import javax.ws.rs.core.Response;
+import javax.ws.rs.ext.Provider;
+
 import java.io.IOException;
 
 /**
  * Mapper for IO exceptions to the BAD_REQUEST response code.
  */
+@Provider
 public class BadRequestMapper extends AbstractMapper<IOException> {
     @Override
     protected Response.Status responseStatus() {