Set country code even when device is not registered on network

Extends the functionality of getNetworkCountryIso to support
no SIM/no service case. When no SIM/no service, it returns
the country code of nearby network (unregistered but cell info
is available to the device).

Test: Manual
Bug: 64335394
Change-Id: Ia32cbc9df9b9adf5d7c24c8b90be20063a94a514