Prevent log input from sending duplicate messages due to file renaming (

elastic#21911)

Input:Log: Reset TTL of registry state when a file is renamed. In some
rare cases the registry state is marked for removal (TTL is set to 0)
while the file is only renamed. Log detects the renaming of the file
and updates the name of the file. As the file still exists it should
also update the TTL of the renamed file.

(cherry picked from commit bb50d32)

filebeat/input/log/input.go

@@ -566,6 +566,7 @@ func (p *Input) harvestExistingFile(newState file.State, oldState file.State) {
 			logp.Debug("input", "Updating state for renamed file: %s -> %s, Current offset: %v", oldState.Source, newState.Source, oldState.Offset)
 			// Update state because of file rotation
 			oldState.Source = newState.Source
+			oldState.TTL = newState.TTL
 			err := p.updateState(oldState)
 			if err != nil {
 				logp.Err("File rotation state update error: %s", err)