Address the low-hanging fruit on report card

[afbjorklund]

Should fix the 99% on https://goreportcard.com/report/github.com/kubernetes/minikube:

minikube/pkg/minikube/tunnel/registry.go
Line 124: error: result of fmt.Errorf call not used (vet)
Line 161: error: result of fmt.Errorf call not used (vet)

minikube/cmd/minikube/cmd/env.go
Line 330: warning: ineffectual assignment to err (ineffassign)

minikube/pkg/gvisor/enable.go
Line 120: warning: "downlaods" is a misspelling of "downloads" (misspell)
minikube/pkg/minikube/console/style.go
Line 96: warning: "embarassed" is a misspelling of "embarrassed" (misspell)

The "gocyclo" complexitiies are left to do, as is "golint" (which even got a separate #3839).

• https://github.com/fzipp/gocyclo

[k8s-ci-robot]

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[afbjorklund]

New score: (make reportcard)

Grade: A+ (99.6%)
Files: 2093
Issues: 68
gofmt: 100%
go_vet: 100%
golint: 97%
gocyclo: 99%
ineffassign: 100%
license: 100%
misspell: 100%