Fix the golint, gosimple warnings

pkg/cluster/cluster.go

pkg/cluster/k8sres.go

pkg/cluster/pg.go

pkg/cluster/pod.go

pkg/cluster/resources.go

pkg/cluster/sync.go

pkg/cluster/util.go

pkg/controller/controller.go

pkg/controller/etcd.go

pkg/controller/postgresql.go

pkg/controller/util.go

pkg/spec/postgresql.go

pkg/spec/types.go

pkg/util/config/config.go

pkg/util/constants/constants.go

pkg/util/k8sutil/k8sutil.go

pkg/util/teams/teams.go

pkg/util/users/users.go

pkg/util/util.go