net/failsafe: fix hotplug alarm cancel

net/failsafe: fix hotplug alarm cancel

The hot-plug alarm mechanism of fail-safe PMD is responsible for
handling removed devices during a plug-out event and to restore them
back to activity following a plug-in event.

Fail-safe sets a flag called "pending_alarm" to validate that only one
alarm callback is pending at any time. While this flag is required to
avoid simultaneous initiations of the alarm thread - it should not be
considered during alarm thread cancellation.

So, when failsafe_hotplug_alarm_cancel() was called while the alarm
callback was being executed the alarm mechanism was not stopped.

Skip checking the "pending_alarm" flag to allow alarm thread
cancellation all the times.

Fixes: ebea83f899d8 ("net/failsafe: add plug-in support")
Cc: stable@dpdk.org
Signed-off-by: Matan Azrad <matan@mellanox.com>
Acked-by: Gaetan Rivet <gaetan.rivet@6wind.com>