fix: expand duplicate poller checks and generalize web server user

Add /etc/crontab and crontab -l -u root to duplicate poller check list;
pollers are sometimes installed via root crontab rather than /etc/cron.d.
Replace Debian-specific 'www-data' note with generic wording that names
both www-data and apache as platform examples.

Signed-off-by: Thomas Vincent <thomasvincent@gmail.com>

Author: somethingwithproof

Debugging.md

@@ -197,7 +197,9 @@ Check for duplicate entries:
 ```sh
 systemctl status cactid
 cat /etc/cron.d/cacti
+cat /etc/crontab
 crontab -l -u cactiuser 2>/dev/null
+crontab -l -u root 2>/dev/null
 ```
 
 The recommended approach is to use the `cactid` systemd service and remove any
@@ -215,7 +217,8 @@ cron entry:
 */5 * * * *  cactiuser  /usr/bin/php -q /var/www/html/cacti/poller.php > /dev/null 2>&1
 ```
 
-Replace `cactiuser` with `www-data` on Debian/Ubuntu systems.
+Replace `cactiuser` with the user your web server runs as (e.g. `www-data` on
+Debian/Ubuntu, `apache` on RHEL-compatible systems).
 
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