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Description of problem:
radvd reports a set of different PIDs in /var/log/messages, pidfile and "ps aux | grep radvd"

Version-Release number of selected component (if applicable):
Found on RHEL 7.5
$ uname -r
3.10.0-862.el7.x86_64

# rpm -qa | grep radvd
radvd-1.9.2-9.el7_5.4.x86_64

How reproducible:
Easy to reproduce.

Steps to Reproduce:
1. Start radvd with minimal functional config file
   radvd -p /tmp/pidfile.pid 
2. Compare pids in
   cat /tmp/pidfile.pid
   tail /var/log/messages 
   ps aux | grep radvd 

Actual results:
# cat pidfile.pid 
17816

# tail /var/log/messages 
Apr 17 14:02:47 host-172-16-36-36 radvd[17813]: version 1.9.2 started

# ps aux | grep radvd
root     17814  0.0  0.0   8612   272 pts/0    S    14:02   0:00 radvd -p /tmp/pidfile.pid
root     17816  0.0  0.0   8612   360 ?        S    14:02   0:00 radvd -p /tmp/pidfile.pid

Expected results:
/var/log/messages should probably contain one of the pids seen in either the pidfile or ps.

Additional info:

"radvd[17813]: version 1.9.2 started" printed on *stdout* prior to fork (and written to logs by systemd) so it contains pid file of parent process.  Daemon doesn't have stdout opened.