test: adjust expecting error for getaddrinfo() under EMFILE

test: adjust expecting error for getaddrinfo() under EMFILE

When getaddrinfo() cannot allocate file descriptor glibc/musl-libc on
linux report EAI_SYSTEM error. But this is not true for freebsd libc [1]
(and hence apple libc [2]), they report EAI_NONAME error instead, so
adjust expectation.

  [1]: https://github.com/freebsd/freebsd/blob/master/lib/libc/net/getaddrinfo.c
  [2]: https://opensource.apple.com/source/Libc/

Refs: #749
Refs: https://github.com/libevent/libevent/issues/749#issuecomment-457838159