Fixed that VT dropped when handover from LTE to IWLAN

Added a workaround so that we don't tear down the data connection
when the old APN list can cover the new APN list, and if we are
not roaming, ignore the roaming protocol field.

Test: Telephony unit tests
bug: 63917285
Change-Id: Ie588f1bc2ef7f38370aa517f0581787d2e4000c9