Partially revert 'SOFTAP: implement SOFTAP new requirement in framework.'

* This commit re-introduced a persistent notification that displays the
  number of connected clients. Remove the persistent notification
  because it shows incorrect information, shows at incorrect times, and
  duplicates the hotspot tethering icon in the signal cluster.
* The functionality to fetch the client count from dnsmasq and broadcast
  remains.

REF: OPO-392
Change-Id: Ie8d99082d6a25d68995d9c7ca3dd2335945f15d5