cmd/coordinator: save CPU by not validating recent .tar.gz snapshots

We were burning a fair bit of CPU here.

Updates golang/go#12671

Change-Id: Iba16e1caa80a1f0b7330098209acaf6d46ce048f
Reviewed-on: https://go-review.googlesource.com/17130
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
1 file changed