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: I8d81c68ab9b4f6f93659542711c081ef1ab0f0b9