Set correct callState for MT/MO call while in Voip Call.

Use case:
Start MO/MT call during VOIP call.

Failure:
Incorrect response sent to AT+CIND? to headset

Root cause:
terminateScoUsingVirtualVoiceCall() resets callState
from INCOMING/DIALING to IDLE. At the same time, if HS sends AT+CIND?
to read call indicators, it will get wrong value of callsetup. This case
is hit only when SCO for VOIP call is not terminated via SDK API call.

Fix:
When VOIP is ended, save current MO/MT call state to
HeadsetPhoneState class to be able to respond with
proper call states when queried by headset.

Change-Id: Ia3a0a2d67dbfffef474de48cab6ee63b82fa4572