Wi-Fi tethering settings are set asynchronously

Wi-Fi tethering settings are set asynchronously

- Issues
  Wi-Fi tethering setting APIs are failed
  while Wi-Fi tethering is being enabled.

- Fix description
  Wi-Fi tethering settings can be modified after Wi-Fi tethering is
  disabled automatically. It makes Wi-Fi tethering settings to be modified
  while Wi-Fi tethering is being disabled.

  But because Wi-Fi tethering state is checked when setting APIs are called,
  setting APIs are failed.

  It is better not to check Wi-Fi tethering state and to provide the way to
  re-load configuration.

  This change only includes "Wi-Fi tethering state is not checked when settings
  are modified".
  Reload configuration change should be provided later.

Change-Id: Iae0514af227fd707773653bde4400cac030b3763