BUG/MEDIUM: standard: Fix memory leak in str2ip2()

BUG/MEDIUM: standard: Fix memory leak in str2ip2()

An haproxy compiled with:

> make -j4 all TARGET=linux2628 USE_GETADDRINFO=1

And running with a configuration like this:

  defaults
  	log	global
  	mode	http
  	option	httplog
  	option	dontlognull
  	timeout connect 5000
  	timeout client  50000
  	timeout server  50000

  frontend fe
  	bind :::8080 v4v6

  	default_backend be

  backend be
  	server s example.com:80 check

Will leak memory inside `str2ip2()`, because the list `result` is not
properly freed in success cases:

==18875== 140 (76 direct, 64 indirect) bytes in 1 blocks are definitely lost in loss record 87 of 111
==18875==    at 0x4C2DB8F: malloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==18875==    by 0x537A565: gaih_inet (getaddrinfo.c:1223)
==18875==    by 0x537DD5D: getaddrinfo (getaddrinfo.c:2425)
==18875==    by 0x4868E5: str2ip2 (standard.c:733)
==18875==    by 0x43F28B: srv_set_addr_via_libc (server.c:3767)
==18875==    by 0x43F50A: srv_iterate_initaddr (server.c:3879)
==18875==    by 0x43F50A: srv_init_addr (server.c:3944)
==18875==    by 0x475B30: init (haproxy.c:1595)
==18875==    by 0x40406D: main (haproxy.c:2479)

The exists as long as the usage of getaddrinfo in that function exists,
it was introduced in commit:
d5f4328efd5f4eaa7c89cad9773124959195430a

v1.5-dev8 is the first tag containing this comment, the fix
should be backported to haproxy 1.5 and newer.