Private SSID is considered

Private SSID is considered

- Issues
  There is no way to set SSID from application.
  "Group Play" client tries to connect to AP which has special SSID.
  There will be similar requirements to implement auto connection feature
  between Wi-Fi AP and station

- Fix description
  Basically device name is used as SSID. But if private SSID is passed through dbus call,
  it is used.

  In tethering_get_wifi_tethering_ssid,
  when Tethering is turned off, device name is returned as SSID;
  when Tethering is turned on, the SSID, which was used to turn on tethering, is returned.

Change-Id: Ia27353693d9b009aed8853b997f35aef86c1a4e6