Bug 1023045 - [Settings][Ringtone][V2.0] The "<" icon of
 sound settings page becomes "X" icon after back from ringtone app.
  - Don't specify "section" when invoking the settings app activity.
Merge pull request #20259 from RudyLu/ringtone/Bug1023045-Sound_backButton

Bug 1023045 - [Settings][Ringtone][V2.0] The "<" icon of
 r=jimporter.