The purpose is to help some process monitor to track the status
of ossec processes. By using number in the pid filename, it is quite
hard to get right pid file/number by some process monitors (like
bluepill or god) -- they can only support static pid filename.
I am not sure if we need to launch multiple instances of ossec.
If that is the case, using pid number in pid filename would help.
However, we may support some option to specify pid file then.
Old pidfile: /var/ossec/var/run/ossec-execd-2132.pid