Fix issue that Wifi Calling preference is showing wrong value.

When showing current Wifi Calling setting, we should decide
whether it's roaming based on telephony.isnetworkRoaming() instead
of checking the roaming button in setting page.

Bug: 67442943
Test: manual
Change-Id: I617cd4709a94ca888318e4903b0cdd2b00f3d84e
Merged-In: I617cd4709a94ca888318e4903b0cdd2b00f3d84e
1 file changed