Automatic merge from submit-queue (batch tested with PRs 42044, 41694, 41927, 42050, 41987)

Simplify and fix hack/{verify,update}-staging-{client-go,godeps}.sh

- merge `hack/{verify,update}-staging-client-go.sh`
- pin godep with shared code
- remove godep-restore completely from the process and replace with a simple check that godeps are restored
- add safety check in `staging/copy.sh` that there is no lingering `k8s.io/apimachinery` in the GOPATH which would lead to inconsistent client-go builds (!)
- check that all these scripts only operate in a clean working dir.