audio policy: bind setMode() and setPhoneState() operations

No routing operation should be allowed between setMode() and setPhoneState()
when starting a call as the audio HAL relies on a precise sequence of mode change
and routing change to select the initial audio device for the call.

Bug: 24083591.

Change-Id: I2d5ef62c11cf7aedc2ec7ca5e5fadd7ac875afbc