In CW Interrogation service class is not sent.

As per 3GPP TS 24.083, section 1.6 UE doesn't need to send service class
parameter in call waiting interrogation  to network. Some networks return error
if service class is sent. So setting service class to SERVICE_CLASS_NONE.

Change-Id: I396963d568573b88795ad2cf1844eb2e047b459e