The commit includes the following fixes:
- do not close the connection until ONHOOK is received from voicemngr.
  this allows DECT handset playing tones from DSP
- cancel the congestion timer in some cases where it was not cancelled
  causing issue of congestion tone being played only for a while when
  the "not existing" number was called
- fix the state of announcement for the case when the announcement was
  played (no sip registration), when account became registered then
  the sub->audio_announcement hanged in a wrong state
- handle the EVENT_CALL_IMMEDIATELY event from voicemngr received with
  full number from DECT and simulate each digit pressed individually