Improve network config validation errors to show which fields are invalid.

Previously, uploading invalid config results in a generic error message
which makes it difficult to figure out what is wrong with the config

Change-Id: I307d2fc0669679b067389c722556eef3aae098b9
diff --git a/web/api/src/main/java/org/onosproject/rest/resources/CoreWebApplication.java b/web/api/src/main/java/org/onosproject/rest/resources/CoreWebApplication.java
index 3a4170b..b8597fa 100644
--- a/web/api/src/main/java/org/onosproject/rest/resources/CoreWebApplication.java
+++ b/web/api/src/main/java/org/onosproject/rest/resources/CoreWebApplication.java
@@ -17,6 +17,7 @@
 package org.onosproject.rest.resources;
 
 import org.onlab.rest.AbstractWebApplication;
+import org.onosproject.rest.exceptions.InvalidConfigExceptionMapper;
 
 import java.util.Set;
 
@@ -49,7 +50,8 @@
                 RegionsWebResource.class,
                 TenantWebResource.class,
                 VirtualNetworkWebResource.class,
-                MastershipWebResource.class
+                MastershipWebResource.class,
+                InvalidConfigExceptionMapper.class
         );
     }
 }