shill: cellular: Add MDN as part of the POST data.

BUG=chrome-os-partner:16151
TEST=Tested the following:
1. Build and run unit tests.
2. Manually verify that the POST data includes MDN.

Change-Id: I7cc3511df1d4333c6d66e7cfe1bd1849b4c06bc7
Reviewed-on: https://gerrit.chromium.org/gerrit/37906
Tested-by: Ben Chan <benchan@chromium.org>
Reviewed-by: Thieu Le <thieule@chromium.org>
Commit-Ready: Ben Chan <benchan@chromium.org>
diff --git a/data/cellular_operator_info b/data/cellular_operator_info
index ddcb987..614d94f 100644
--- a/data/cellular_operator_info
+++ b/data/cellular_operator_info
@@ -9,4 +9,4 @@
 [311480]
 OLP.URL=https://quickaccess.verizonwireless.com/bbportal/chrome/start4g.do
 OLP.Method=POST
-OLP.PostData=oem=GOG3&iccid=${iccid}&imei=${imei}
+OLP.PostData=oem=GOG3&iccid=${iccid}&imei=${imei}&mdn=${mdn}