Add operation context to user-facing error messages

Prefix raw err.Error() strings surfaced in CR statuses and CLI stderr with the failed operation.

Signed-off-by: chlins <chlins.zhang@gmail.com>
(cherry picked from commit e03ff894ff)

pkg/cmd/errors.go

@@ -27,7 +27,7 @@ import (
 func CheckError(err error) {
 	if err != nil {
 		if err != context.Canceled {
-			fmt.Fprintf(os.Stderr, "An error occurred: %v\n", err)
+			fmt.Fprintf(os.Stderr, "velero: %v\n", err)
 		}
 		os.Exit(1)
 	}