Eliminate logspam using filelog monitor

When using a filelog monitor, the top-level `pluginConfig.message` filter provides a limited stream of log events to be checked against the `rules[].pattern`.  I thus expect it to be normal for most log events to fail to match the top-level `pluginConfig.message` filter. Such a condition should not trigger a warning-level log message.  And in fact such log messages should be suppressed by default, unless `-v=5` or higher is used for troubleshooting/debug purposes.

Author: skaven81

pkg/systemlogmonitor/logwatchers/filelog/log_watcher.go

@@ -121,7 +121,7 @@ func (s *filelogWatcher) watchLoop() {
 		}
 		log, err := s.translator.translate(strings.TrimSuffix(line, "\n"))
 		if err != nil {
-			klog.Warningf("Unable to parse line: %q, %v", line, err)
+			klog.V(5).Infof("Unable to parse line: %q, %v", line, err)
 			continue
 		}
 		// Discard messages before start time.