If the service is controlled by xinetd, then another instance is started each time a new connection if made. Check how vsftp is run.
It may be started normally in runlevels 3 and 5 but have an /etc/xinetd.d/vsftpd configuration file as well.
If so, you could run "sudo /sbin/chkconfig vsftpd off" and then "sudo /sbin/chkconfig vsftpd xinetd".
The second entry will simply delete the "disable = yes" line which you could do yourself.
# default: off
# The vsftpd FTP server serves FTP connections. It uses
# normal, unencrypted usernames and passwords for authentication.
# vsftpd is designed to be secure.
# NOTE: This file contains the configuration for xinetd to start vsftpd.
# the configuration file for vsftp itself is in /etc/vsftpd.conf
socket_type = stream
protocol = tcp
wait = no
user = root
server = /usr/sbin/vsftpd
# server_args =
# log_on_success += DURATION USERID
# log_on_failure += USERID
# nice = 10