set needed config option to startup

package/vsftpd/files/vsftpd.conf

@@ -15,3 +15,4 @@ syslog_enable=YES
 #xferlog_enable=YES
 #xferlog_file=/var/log/vsftpd.log
 #xferlog_std_format=YES
+secure_chroot_dir=/var/run/vsftpd