net/failsafe: support device removal

Listen to INTR_RMV events issued by slaves.
Add atomic flags on slave queues to detect use of slave bursts function.
If a removal is detected, set the recollection flag on this slave.

During a slave upkeep round, if its recollection flag is set and its
burst functions are not in use by any thread, remove that slave.

Signed-off-by: Gaetan Rivet <gaetan.rivet@6wind.com>
Acked-by: Olga Shern <olgas@mellanox.com>