Switches interruptiveness setting icon in notification menu.

This change modifies the icon show in the notification menu row for
interruptiveness settings (either a bell or a crossed-out bell) to show
the current state of the notification instead of the opposite state,
since the button is no longer a direct toggle.

Test: manual
Change-Id: I2de79af093a0e138e00d234d6fa745b79c25815c