callwaiting: Support cdma call waiting setting

CDMA call waiting should be supported by setting UI
regarding CDMA VoLTE case.
Getting query call waiting is useless in no VoLTE case.
SS_STATUS_UNKNOWN will be returned for empty result.
Place call to set call waiting with prefix.

Bug: 146533000

Change-Id: Ib8b580781154543c87269786c8ecf9cf71d0d93b
Signed-off-by: Jang Hayeong <hayeong.jang@samsung.com>
Signed-off-by: Sungjae <sung_jae.kim@samsung.com>