System logs are empty (/var/log/messages; /var/log/secure; etc)

well... almost 2 years had gone by and finally found the solution for the issue. If anyone has the same issue please try the steps below.

syslogd version rsyslogd 8.24.0-38.el7

The issue was related to the imjournal module. I've remove all the entries of the rsyslog.conf related to imjournal and switched the OmitLocalLogging to off

After that I've restarted the rsyslog service using systemctl restart rsyslog and the log entries started to be populated to the log file that I've configured in rsyslog.conf.

The rsyslog.conf file now looks like this:

$ModLoad imuxsock
#$ModLoad imjournal
$ModLoad immark 
$WorkDirectory /var/lib/rsyslog
$ActionFileDefaultTemplate RSYSLOG_TraditionalFileFormat
$IncludeConfig /etc/rsyslog.d/*.conf
$OmitLocalLogging off
#$IMJournalStateFile imjournal.state
*.info;mail.none;authpriv.none;cron.none                /var/log/messages
authpriv.*                                              /var/log/secure
mail.*                                                  -/var/log/maillog
cron.*                                                  /var/log/cron
*.emerg                                                 :omusrmsg:*
uucp,news.crit                                          /var/log/spooler
local7.*                                                /var/log/boot.log
local3.*                                                /var/log/sshd-second.log