Make polled request timeout less invasive.

Instead of panic after one second of polling, make the normal timeout
handler to activate, reset the controller and abort the outstanding
requests. If all of it won't happen within 10 seconds then something
in the driver is likely stuck bad and panic is the only way out.

In particular this fixed device hot unplug during execution of those
polled commands, allowing clean device detach instead of panic.

MFC after: 1 week
Sponsored by: iXsystems, Inc.