request timeout issue

The way to handle a request that timeout is broken:

• there is two different timeouts: 1 second for an APU request and 15 seconds to get a VirtIO buffer
• in case of timeout, if the application ignore it, we don't release correctly all the resources (at somepoint, we can't allocate a VirtIO buffer)
• the firmware never get notified of timeout an keep executing the request (and never handle new ones)
• no way to configure the timeout which could needed if a request take too long to execute