Fixed handling of bargein and dtmfBargein parameters.

[dmitrikozlov]

This change fixes the following test cases

let say = {
      text: text,
      synthesizer: googleSpeech,
    };
let recognizer = {
        vendor: 'google',
        language: 'en-US',
      };
let promptParams = {
      actionHook: '/loop',
      input: ['digits', 'speech'],
      timeout: 10,
      say: say,
      recogniser: recognizer,
}

Case 1

let promptParams = {
      dtmfBargein: false,
      maxDigits:1,
    };

Expected: Bargein with DTMF doesn’t happen
Result Bargein with either DTMF or speech still happens

Case 2

let promptParams = {
      bargein: false,
      dtmfBargein: false,
      maxDigits:1,
    };

Expected: Bargein with DTMF or Speech doesn’t happen
Result Barge-in with either DTMF or speech still happens

Case 3

let promptParams = {
      listenDuringPrompt: true,
      bargein: true,
      dtmfBargein: true,
      maxDigits:1,
    };

Expected: User can bargein prompts with DTMF or speech. Bardein happens almost immediately after a DTMF or speech input.

Result: Bargein with DTMF works as expected; Bargein with speech behaves badly. Sometimes bargein happens on no speech input—background noise? Sometimes prompts are interrupted either on the first spoken word or on the second or even third. The user app may receive all of the spoken words or only the first spoken word when interrupted after the second spoken word.

Case 4

let promptParams = {
      listenDuringPrompt: true,
      bargein: false,
      dtmfBargein: false,
      maxDigits:1,
    };

Expected: prompt plays to the end
Result: prompt interrupted with either speech or DTMF.

[davehorton]

@xquanluu need your review here