accounting: fix global error acounting

fs.CountError is called when an error is encountered. The method was
calling GlobalStats().Error(err) which incremented the error at the
global stats level. This led to calls to core/stats with group= filter
returning an error count of 0 even if errors actually occured.

This change requires the context to be provided when calling
fs.CountError. Doing so, we can retrieve the correct StatsInfo to
increment the errors from.

Fixes #5865

fs/walk/walk.go

@@ -170,7 +170,7 @@ func listRwalk(ctx context.Context, f fs.Fs, path string, includeAll bool, maxLe
 		// Carry on listing but return the error at the end
 		if err != nil {
 			listErr = err
-			err = fs.CountError(err)
+			err = fs.CountError(ctx, err)
 			fs.Errorf(path, "error listing: %v", err)
 			return nil
 		}
@@ -415,7 +415,7 @@ func walk(ctx context.Context, f fs.Fs, path string, includeAll bool, maxLevel i
 					// NB once we have passed entries to fn we mustn't touch it again
 					if err != nil && err != ErrorSkipDir {
 						traversing.Done()
-						err = fs.CountError(err)
+						err = fs.CountError(ctx, err)
 						fs.Errorf(job.remote, "error listing: %v", err)
 						closeQuit()
 						// Send error to error channel if space