added CentOS 8 detection to monitoring tools

server/lib/classes/monitor_tools.inc.php

@@ -319,6 +319,14 @@ class monitor_tools {
 			} else {
 				$distid = 'centos72';
 			}
+                } elseif(stristr($content, 'CentOS Linux release 8')) {
+                        preg_match_all('/([0-9]{1,2})\.?([0-9]{0,2})\.?([0-9]*)/', $content, $version);
+                        $distname = 'CentOS';
+                        $distver = is_array($version)? implode('.', array_filter(array($version[1][0],$version[2][0],$version[3][0]),'strlen')) :'Unknown';
+                        $distbaseid = 'fedora';
+                        $var=explode(" ", $content);
+                        $var=explode(".", $var[3]);
+                        $var=$var[0].".".$var[1];
 		} else {
 			$distname = 'Redhat';
 			$distver = 'Unknown';