io: fix maybe-uninitialized warning in test (-O2)

/home/rusty/devel/cvs/ccan/ccan/io/test/run-01-start-finish.c: In function ‘main’:
/home/rusty/devel/cvs/ccan/ccan/io/test/run-01-start-finish.c:89:7: warning: ‘addrinfo’ may be used uninitialized in this function [-Wmaybe-uninitialized]
   if (connect(fd, addrinfo->ai_addr, addrinfo->ai_addrlen) != 0)

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>