hal: Fix for Tx Mute issue when a new call accepted while in call

- While in a voice call, if an incoming call is accepted, Tx path
  is muted on some specific networks.
- If there is an incoming call, Telephony sets the mode to RINGTONE,
  and the condition check in audio HAL leads to voice call tear
  down. When the call is accepted, the mode is set back to
  IN_CALL and voice call path is re-enabled but the voice drivers
  will be operating with default settings as there is no notification
  from Modem side in this case. For modem, there is no change
  in the call state i.e. just switched from caller 1 to caller2.
- Fix the issue by ensuring that the voice call is teared down
  only if mode is set to NORMAL while call is progress.

Change-Id: Iac5c4d2e6852ccda0da2ea13927d2a95bfb6938b