Make the silent/vibrate status icon reflect overall device state. (DO NOT MERGE)

Previously, this status icon reflected just the incoming
call behavior:
 - gone for audible (with or without vibrate),
 - wiggling phone for vibrate,
 - silent (speaker + X) for no audible ring or vibrate.

Now that silent mode has changed (see VIBRATE_IN_SILENT),
you can easily get into a state where this icon is
confusing by setting the incoming call ringer to *never*
vibrate but setting the overall device silent state to allow
vibration (VIBRATE_IN_SILENT=true).  In this case, rocking
the volume all the way down would show a wiggling phone
(because the device is in vibrate-only mode) but the status
bar would show speaker+X (because the incoming call would
neither ring nor vibrate).

Now these two icons are consistent. This means, however,
that if this special condition is set by the user (device
vibrates in silent mode, but incoming calls should never
vibrate) and the device is in silent mode, the status bar
will show a wiggling phone even though incoming calls will
not vibrate the device. This puts the ringer on a more even
footing with other apps on the device, which may elect not
to vibrate even if VIBRATE_IN_SILENT=true overall.

Bug: 2598014
Change-Id: Ib942f68738d77ab0d9b9da4fac718ae5957c133c