MSIM: Select preferred apn based on subscription id.

While querying and setting preferred apn in APN settings,
use the PREFERRED_APN_URI based on current subscription id.
This will make sure that the preferred apn is selected
correctly based on the SIM card selected.

Change-Id: I826295f993d99b6f1fafbab9ad7dba9cad04ffbb
CRs-Fixed: 958420