apns-conf.xml: Re-add old StraightTalk ATT apn settings

In some areas, the new StraightTalk ATT apn settings do
not work, requiring the user to re-add the apn settings
on their own, a feat made more difficult by the fact
that StraightTalk only lists the new apn info on their
website

Change-Id: Id02876d4aa461a3ad8e7211ef45f468b6e181036