adb: close ep0 on disconnection.

adbd on device kicks the usb connection when usb IO fails. But to notify
adb on host to reconnect it, adbd needs to close ep0 to reset the usb
connection. Otherwise, adb on host cann't connect the device unless the
usb cable is reconnected or adb host server is restarted.

This can be tested by using `adb reconnect device` command.

Bug: 25935458

Change-Id: I80979d6029e60b9cfd218f7b9b5201810238ec07
(cherry picked from commit 69e97e4b)