shill: Turn on dual-stack IPv4v6 for Rakuten

BUG=b:186475134
TEST=unit tests. Live tests to be done by partners on jinlon and/or
Rakuten.

Change-Id: I17857ca5c7b91bf933106224852c25113607a7c1
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform2/+/2852718
Tested-by: Hugo Benichi <hugobenichi@google.com>
Auto-Submit: Hugo Benichi <hugobenichi@google.com>
Reviewed-by: Eric Caruso <ejcaruso@chromium.org>
Commit-Queue: Hugo Benichi <hugobenichi@google.com>
diff --git a/shill/mobile_operator_db/serviceproviders.prototxt b/shill/mobile_operator_db/serviceproviders.prototxt
index 40a3fc6..ce88f04 100644
--- a/shill/mobile_operator_db/serviceproviders.prototxt
+++ b/shill/mobile_operator_db/serviceproviders.prototxt
@@ -7571,6 +7571,7 @@
     mobile_apn {
       apn : "rakuten.jp"
       is_attach_apn : true
+      ip_type : IPV4V6
     }
   }
 }