net/failsafe: fix probe cleanup

net/failsafe: fix probe cleanup

The hot-plug alarm mechanism is responsible to practically execute both
plug in and out operations. It periodically tries to detect missed
sub-devices to be reconfigured and clean the resources of the removed
sub-devices.

The hot-plug alarm is started by the failsafe probe function, and it's
wrongly not stopped if failsafe instance got an error. for example
when starting failsafe with a MAC option, and giving it an invalid MAC
address this will lead to a NULL pointer for the dev private field. Then
when the hotplug alarm is called it will try to access this pointer,
which will lead to a segmentation fault.

Uninstall the hot-plug alarm in case of error in probe function.

Fixes: ebea83f8 ("net/failsafe: add plug-in support")
Cc: stable@dpdk.org
Signed-off-by: Raslan Darawsheh <rasland@mellanox.com>
Acked-by: Matan Azrad <matan@mellanox.com>
Acked-by: Gaetan Rivet <gaetan.rivet@6wind.com>