test-getaddrinfo: report error information

test-getaddrinfo: report error information

Clang deduced that if ENABLE_DEBUGGING is undefined, then err
was a dead assignment.  But in the EAI_SYSTEM case, we fail
the test, so the output should be unconditional.

* tests/test-getaddrinfo.c (simple): Use err outside of dbprintf.

Signed-off-by: Eric Blake <eblake@redhat.com>