IMS-VT: Pop up request "video" message when request voice call

Do not display requesting for all downgrade use-cases
such as VT to VT-TX or VT-RX or Voice only.
VT-TX or VT-RX to Voice only.

Change-Id: I3714f82acb1eccb3d99aea3c2fbc18ab04af1714
CRs-Fixed: 2018550
2 files changed