Add action to sync all Registrar RDAP base URLs from the ICANN endpoint

We aren't turning on the cron job yet - we want to make sure it works correctly first.

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=252726789

java/google/registry/env/common/backend/WEB-INF/web.xml

@@ -309,6 +309,12 @@
     <url-pattern>/_dr/task/resaveAllEppResources</url-pattern>
   </servlet-mapping>
 
+  <!--  Reread all Registrar RDAP Base Urls from the ICANN endpoint. -->
+  <servlet-mapping>
+    <servlet-name>backend-servlet</servlet-name>
+    <url-pattern>/_dr/task/updateRegistrarRdapBaseUrls</url-pattern>
+  </servlet-mapping>
+
   <!--  Action to re-save a given entity. -->
   <servlet-mapping>
     <servlet-name>backend-servlet</servlet-name>