am 13f6270e: SipAudioCall: use SipErrorCode instead of string in onError()

Merge commit '13f6270eb14b409709c936b828e2a2fd40e427c4' into gingerbread-plus-aosp

* commit '13f6270eb14b409709c936b828e2a2fd40e427c4':
  SipAudioCall: use SipErrorCode instead of string in onError()