Extend ubus calls between voicemngr and asterisk and dectmngr, REF 14666

Yalu Zhangrequested to merge
14666-no-g722 into voicemngr_rdkb 
The following ubus RPC calls are extended.
- ubus call asterisk event: add a data parameter with value "narrow_band_only" to
  event OFFHOOK for FXS and DECT handset which doesn't support wide band codecs.
- ubus call endpt call: add a data parameter with value "narrow_band_only" to start
  an outgoing call or accept an incoming call from a DECT handset which doesn't
  support wide band codecs.

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