- added helper script
  from kubernetes/kubernetes#79384 (comment)
  to scripts/upgrade-k8s.sh

- removed bashisms from the script

Signed-off-by: Ed Bartosh <[email protected]>

- upgraded to Kubernetes 1.25.0:
  $ ./scripts/upgrade-k8s.sh 1.25.0
  go: downloading k8s.io/kubernetes v1.25.0
  go: upgraded k8s.io/api v0.25.0-rc.0 => v0.25.0
  go: upgraded k8s.io/apimachinery v0.25.0-rc.0 => v0.25.0
  go: upgraded k8s.io/apiserver v0.25.0-rc.0 => v0.25.0
  go: upgraded k8s.io/component-base v0.25.0-rc.0 => v0.25.0
  go: upgraded k8s.io/component-helpers v0.25.0-rc.0 => v0.25.0
  go: upgraded k8s.io/kubernetes v1.25.0-rc.0 => v1.25.0

Signed-off-by: Ed Bartosh <[email protected]>

Removed unused import. This should fix this golangci-lint failure:
  can't run linter goanalysis_metalinter:
  buildir: failed to load package :
  could not load export data:
  no export data for "cloud.google.com/go/compute/metadata"

Signed-off-by: Ed Bartosh <[email protected]>