net/failsafe: use ownership mechanism for slaves

net/failsafe: use ownership mechanism for slaves

Fail-safe PMD sub devices management is based on ethdev port mechanism.
So, the sub-devices management structures are exposed to other DPDK
entities which may use them in parallel to fail-safe PMD.

Use the new port ownership mechanism to avoid multiple managments of
fail-safe PMD sub-devices.

Signed-off-by: Matan Azrad <matan@mellanox.com>
Acked-by: Gaetan Rivet <gaetan.rivet@6wind.com>