Fixes rp2 issue where socket.getaddrinfo() could block indefinitely if an
interface goes down and still has a DNS server configured, as the LWIP
timer stops running and can't time out the DNS query.
Adds a regression test under multi_wlan that times out on rp2 without this
fix.
Fixes issue #18797.
This work was funded through GitHub Sponsors.
Signed-off-by: Angus Gratton <angus@redyak.com.au>