Joystick USB disconnect is non-recoverable.

To reproduce:
while using USB joystick, pull the USB plug.
on reconnect, it won't work.
module unload joystick
Note: even now, MANUAL_CONTROL packets are produced, prohibiting pilot from using RC.
module load joystick
won't help
- user needs to terminate and restart MAVProxy to regain joystick / MANUAL_CONTROL

Reproduce the issue in MAVProxy by disconnecting and reconnecting a USB joystick, then try unloading and loading the joystick module as described. Trace the joystick handling and MANUAL_CONTROL behavior around disconnect and reconnect; done means the joystick recovers without restarting MAVProxy and stale MANUAL_CONTROL packets no longer prevent RC use.

Written by the indexing model from the issue text.