setWfcSetting: set WFC mode w.r.t. roaming state

When turing on WFC, WFC mode in modem should also be updated
to user set WFC mode: roaming mode if in roaming network or
home mode otherwise.

The code was using home mode always; so it causes user setting
mismatch with modem setting in roaming, if home mode is different
from roaming mode.

Bug: 77882002
Test: manual - force device in roaming state, and turn on WFC;
      verify that modem uses roaming mode not home mode.

Change-Id: I510aa469736de7a9262a87ec6399f5ca97cb3af1