Bug 915081 - Hide the end-and-answer button during CDMA call waiting

- Removed the end-and-answer button when in CDMA call waiting mode as it
  does not support ending the first call and answering the other one,
  the hold-and-answer button is enlarged to fill up the entire container
  under these conditions
- Refactored the CDMA CSS code
- Added unit-tests covering the changes