don't scream when auto-selected IPv6 is not available

when --bind-address is not specificed explicitly (or set to '*')
MariaDB tries all wildcard addresses. Print a warning (not an error)
if a socket cannot be created for some of them.

Still print an error if a socket cannot be created for an address
that a user has specified expicitly with --bind-address.

sql/mysqld.cc

@@ -2423,10 +2423,11 @@ static MYSQL_SOCKET activate_tcp_port(uint port)
 
     if (mysql_socket_getfd(ip_sock) == INVALID_SOCKET)
     {
-      sql_print_error("Failed to create a socket for %s '%s': errno: %d.",
-                      (a->ai_family == AF_INET) ? "IPv4" : "IPv6",
-                      (const char *) ip_addr,
-                      (int) socket_errno);
+      sql_print_message_func func= real_bind_addr_str ? sql_print_error
+                                                      : sql_print_warning;
+      func("Failed to create a socket for %s '%s': errno: %d.",
+           (a->ai_family == AF_INET) ? "IPv4" : "IPv6",
+           (const char *) ip_addr, (int) socket_errno);
     }
     else 
     {