USB: AppOps: always show "USB connection" when usb connected

If no mode is chosen, "USB computer connection" will be hidden.
Unfortunately, there is no default mode, so users can't find it
by dragging down the statusbar. For better user experience, we export it
to users when usb connected.

Change-Id: I486e1a012f12f81f5a79d5f3686db58f980c0890