Telephony: Ignore data registration when bringing down call

Bring down data call even if we have it while data registration indicates
phone is in unregistered state.
getAnyDataEnabled will return false if phone is not registered hence
user disabling data while phone is unregistered will have no effect
(and data call will remain there indefinitely).

Change-Id: I72cf1fb8b89cad5bb8595233721d1ac315750dbf
CRs-Fixed: 372219