telephony: Support mvno tethering apn through config_tether_apndata.

The GSMDCT already has classfication of mvno operator in createApnList().
But, fetchDunApn() funtion has no consideration about mvno operator.
So it needs to be implemented for mvno operator.
As qualifier could not be classified by mvno parameter, the resource
should be changed to support multiple apns by one mcc/mnc.

The modified fetchDunApn() returns matched mvno apn or normal(not mvno) apn

Bug: 10096119
Change-Id: I5aa41d2addfb9499f7cde123b55acf1e9e64931b