Fix network_accept_any test suite on Hurd

[Julien-Elie]

Failed Set                 Fail/Total (%) Skip Stat  Failing Tests
-------------------------- -------------- ---- ----  ------------------------
lib/network/server            8/42    19%    0   --  35-42

$ ./runtests -o lib/network/server
ok 1 - IPv4 server test
ok 2 - ...socket accept
ok 3 - ...socket read
ok 4 - client made correct connections
[...]
ok 9 - IPv6 server test
ok 10 - ...socket accept
ok 11 - ...socket read
ok 12 - client made correct connections
[...]
ok 17 - all address server test (part 1)
ok 18 - ...socket accept
ok 19 - ...socket read
ok 20 - client made correct connections
ok 21 - all address server test (part 2)
ok 22 - ...socket accept
ok 23 - ...socket read
ok 24 - client made correct connections
[...]
ok 33 - network_accept_any test
ok 34 - ...socket accept
Segmentation fault         ./runtests -o lib/network/server

Reading data fails for network_accept_any.