cmd: use slices.Equal to simplify code

cmd: use slices.Equal to simplify code

#57433 added slices.Equal, using it can reduce the amount of code

Change-Id: I70d14b6c4c24da641a34ed36c900d9291033f526
Reviewed-on: https://go-review.googlesource.com/c/go/+/492576
Reviewed-by: Than McIntosh <thanm@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Run-TryBot: Ian Lance Taylor <iant@google.com>
Reviewed-by: Ian Lance Taylor <iant@google.com>
Auto-Submit: Ian Lance Taylor <iant@google.com>
Run-TryBot: shuang cui <imcusg@gmail.com>