apns: remove default- and dun-types for Verizon MMS 31x/48x

Remove the default- and dun-types set on the Verizon MCC=31x
and MNC=48x pairs. This fixes long connection delays to
LTE and EHRPD apns.

It is based on: http://review.cyanogenmod.org/#/c/61711/

Change-Id: Ib39c601cb3610ff972db3849dfc96542f75f5761
Merge pull request #8 from CyanogenMod/cm-11.0

apns: remove default- and dun-types for Verizon MMS 31x/48x