rpc: getaddrinfo: also accept IPv4-mapped IPv6 addresses

If only IPv6 is configured on the host, getaddrinfo with AI_ADDRCONFIG
in hints would return EAI_ADDRFAMILY for nodenames that resolve to IPv4.

Also pass AI_V4MAPPED to accept IPv4-mapped addresses on IPv6-only
systems.
Signed-off-by: NZhimin Feng <fengzhimin1@huawei.com>
[rewrote the commit message - jtomko]
Signed-off-by: NJán Tomko <jtomko@redhat.com>
Reviewed-by: NJán Tomko <jtomko@redhat.com>
Reviewed-by: NDaniel P. Berrangé <berrange@redhat.com>

src/rpc/virnetsocket.c

@@ -575,7 +575,7 @@ int virNetSocketNewConnectTCP(const char *nodename,
 
     memset(&hints, 0, sizeof(hints));
     hints.ai_family = family;
-    hints.ai_flags = AI_PASSIVE | AI_ADDRCONFIG;
+    hints.ai_flags = AI_PASSIVE | AI_ADDRCONFIG | AI_V4MAPPED;
     hints.ai_socktype = SOCK_STREAM;
 
     int e = getaddrinfo(nodename, service, &hints, &ai);