Reduce messages severity from error to warning. Occurred events don't…

… interrupt collecting metrics, hence could be considered as warnings.

internal/collector/filesystem_common.go

@@ -60,7 +60,7 @@ func parseProcMounts(r io.Reader, filters map[string]filter.Filter) ([]mount, er
 // truncateDeviceName truncates passed full path to device to short device name.
 func truncateDeviceName(path string) string {
 	if path == "" {
-		log.Warnf("empty path passed")
+		log.Warnf("cannot truncate empty device path")
 		return ""
 	}
 	// Make name which will be returned in case of later errors occurred.
@@ -70,15 +70,15 @@ func truncateDeviceName(path string) string {
 	// Check device path exists.
 	fi, err := os.Lstat(path)
 	if err != nil {
-		log.Errorf("stat device path %s failed: %s, use defaults (%s)", path, err, name)
+		log.Warnf("%s, use default '%s'", err, name)
 		return name
 	}
 
 	// If path is symlink, try dereference it.
 	if fi.Mode()&os.ModeSymlink != 0 {
 		resolved, err := os.Readlink(path)
 		if err != nil {
-			log.Errorf("dereference device path %s failed: %s, use name's last part (%s)", path, err, name)
+			log.Warnf("%s, use name's last part '%s'", err, name)
 			return name
 		}
 		// Swap name to dereferenced origin.