cockroachkvs: minor updates

[RaduBerinde]

Bringing in a few comments from the CRDB code.

Informs 139068

[cockroach-teamcity]

This change is 

[jbowens]

Reviewed 1 of 1 files at r1, all commit messages.
Reviewable status: all files reviewed, 1 unresolved discussion (waiting on @RaduBerinde)

---

cockroachkvs/cockroachkvs.go line 235 at r1 (raw file):

	if versionLen > len(key) {
		panic(errors.AssertionFailedf("invalid version length"))
	}

I'm forgetting, did we remove this assertion from the cockroach repo and do you remember why?

[RaduBerinde]

Reviewable status: all files reviewed, 1 unresolved discussion (waiting on @jbowens)

---

cockroachkvs/cockroachkvs.go line 235 at r1 (raw file):

Previously, jbowens (Jackson Owens) wrote…

I'm forgetting, did we remove this assertion from the cockroach repo and do you remember why?

Yeah, it's not there. Maybe some concern with overhead due to the panic call. In practice we will crash right after in this case anyway so I don't think it is too useful (and we check it above in invariants mode).

[RaduBerinde]

CI ran into a TestWALFailoverRandomized flake (could not open manifest file "MANIFEST-000144" for DB "primary") but I couldn't reproduce.