MDEV-37098 Fix Spider test failures in network-less environments

MDEV-37098 Fix Spider test failures in network-less environments

When running tests in environments without a network interface (such as
containers with `--network=none`), Spider could not retrieve a hardware
address to generate a node ID. This triggered a warning in the server
log, causing MTR to fail the test due to unexpected output:

    [Warning] mariadbd: Can't get hardware address with error 2

Fix this by logging Spider hardware address errors to server log only.
This ensures the message is recorded in the server log for debugging but
does not pollute the client output.

It is questionable if this is a problem at all anyway, as when
`my_gethwaddr` fails, the code zeroes out the address buffer, resulting
in a `spider_unique_id` formatted like `-000000000000-PID-`, which is
valid.

Forwarded: https://github.com/MariaDB/server/pull/4479

Gbp-Pq: Name MDEV-37098-Spider-test-failures-in-network-less-environments.patch