Implement setVisualVoicemailEnabled()

This CL allows the default dialer/apps with carrier privileges/apps
with MODIFY_PHONE_STATE permission enable or disable the visual
voicemail client.

+ Fix the bug where the configuration state error was not cleared
  for subsequent activation due to the edit was not applied.

Bug: 30709089
Change-Id: Ie3e4a8b48a6862e10b7381520d07d0f879b1884b
4 files changed