more fixes on safe volume warning message

Fixes the following problems with safe headphone volume warning message:
- Do not display the warning dialog when screen is off.
- Use the same 3 second timeout as for the volume slider to dismiss the dialog.
- Do not dismiss the warning dialog when touching outside of the slider window
but inside the warning window.
- Disable the volume slider when the warning message is displayed.
- When setting volume directly (touching the volume slider), and the warning
is displayed, save the requested volume and apply it if acknowledged by the user.
- Do not display the warning message when restoring safe volume after 20h of
cumulative listenening

Bug 7658641.

Change-Id: Ib3d1315193a433dad918aa5df78fa071062b2394