Don't close USB type notification when USB is connected to USB devices.

Previously we show a notificatino to show the UsbModeChooser when
Android is connected to another Android via USB type C cable.
However UsbModeChoooser activity was closed immediately after a user
tapped the notification, if the Android worked as host.

FIXED=27535640

Change-Id: I707dcbf1021e7381096c0ae7cc2d712892ac5a5a