Fix a race condition between port stop and error recovery task. When io
forwarding is not started on Stingray devices, driver will not receive
the async event from FW when there is a FW reset. While exiting testpmd,
as part of port stop driver sees this event and this in turn causes a
race between port stop and error recovery task.
Fixed this by ignoring the fatal/non-fatal async event from FW while
stopping port.