DialAction is not executed when everyone is busy

[ghjansen]

Related to issues #2271, #2432 and PR #2420.

Scenario:

• Restcomm creates multiple outbound calls through a Dial forking RCML like:

<Response>
  <Dial timeLimit="1000" timeout="2" action="http://127.0.0.1:8090/test">
    <Number>+131313</Number>\
    <Uri>sip:[email protected]:5092</Uri>
    <Client>alice</Client>
  </Dial>
</Response>

• each one of the call branches answers back with SIP 486 (BUSY)

Failure:

• no request is received at the action address informed

This issue was noticed only after the optimisation of the patch implemented at #2432

[ghjansen]

Solution:
Prevented VoiceInterpreter to move to the next verb when MediaGroupResponse is received, if action attribute is different than null.

Closed via PR #2420 .