Fix bad attribute name vs carrier for Giffgaff MMS.

It seems such entries are coming from apps like APN backup&restore,
which have a slightly different format.

Change-Id: I51d949e4dc13e832c84ecccd66cd9cd723ea2ec4

prebuilt/common/etc/apns-conf.xml

@@ -194,7 +194,7 @@
   <apn carrier="O2 MOBILE WEB" mcc="234" mnc="02" apn="mobile.o2.co.uk" user="O2web" password="O2web" type="default,supl" />
   <apn carrier="O2 MMS Prepay" mcc="234" mnc="02" apn="payandgo.o2.co.uk" user="payandgo" password="password" mmsc="http://mmsc.mms.o2.co.uk:8002" mmsproxy="193.113.200.195" mmsport="8080" type="mms" />
   <apn carrier="O2 MMS Postpay" mcc="234" mnc="02" apn="wap.o2.co.uk" user="o2wap" password="password" mmsc="http://mmsc.mms.o2.co.uk:8002" mmsproxy="193.113.200.195" mmsport="8080" type="mms" />
-  <apn name="Giffgaff" numeric="23410" mcc="234" mnc="10" apn="giffgaff.com" user="giffgaff" server="http://mmsc.mediamessaging.co.uk:8002" password="password" proxy="" port="" mmsproxy="193.113.200.195" mmsport="8080" mmsprotocol="null" mmsc="http://mmsc.mediamessaging.co.uk:8002" type="default,supl,mms" />
+  <apn carrier="Giffgaff" mcc="234" mnc="10" apn="giffgaff.com" user="giffgaff" server="http://mmsc.mediamessaging.co.uk:8002" password="password" mmsproxy="193.113.200.195" mmsport="8080" mmsc="http://mmsc.mediamessaging.co.uk:8002" type="default,supl,mms" />
   <apn carrier="O2 UK MMS" mcc="234" mnc="10" apn="idata.o2.co.uk" user="vertigo" password="password" mmsc="http://mmsc.mms.o2.co.uk:8002" mmsproxy="193.113.200.195" mmsport="8080" type="mms" />
   <apn carrier="O2 UK" mcc="234" mnc="10" apn="mobile.o2.co.uk" user="O2web" password="O2web" type="default,supl" />
   <apn carrier="O2 UK" mcc="234" mnc="10" apn="mobile.o2.co.uk" user="vertigo" type="default,supl,mms" />