Always use 0 when getting the address for getaddrinfo

This matches what all versions of Python do and reverts
https://github.com/gevent/gevent/commit/9b1bccffc11455112076189f35023291cf97a2a2

The bug that commit references was marked as "won't fix". This is part
of an effort to adapt to changes in 3.7b2 that lead us to produce a
different errno than the system does for
`socket.create_connection(('localhost', ...))`

src/gevent/socket.py

@@ -75,7 +75,7 @@ def create_connection(address, timeout=_GLOBAL_DEFAULT_TIMEOUT, source_address=N
     host, port = address
     # getaddrinfo is documented as returning a list, but our interface
     # is pluggable, so be sure it does.
-    addrs = list(getaddrinfo(host, port, 0 if has_ipv6 else AF_INET, SOCK_STREAM))
+    addrs = list(getaddrinfo(host, port, 0, SOCK_STREAM))
     if not addrs:
         raise error("getaddrinfo returns an empty list")