Add USB_HOST_CONNECTED extra to ACTION_USB_STATE sticky intent.

Previously UsbModeChooser activity is automatically closed when Android
is connected to another Android and works as host. This is because
ACTION_USB_STATE intent does not include the information whether Android
is connected as host and UsbModeChooser regards Android is not connected
USB devices.

The CL introduce the HOST_CONNECTED extra to ACTION_USB_STATE so that
UsbModeChooser can refer it.

BUG=27535640

Change-Id: Ie29583b78319078430f6d9a8390787780410ac8c