Update cortex vendor to grafana/cortex:yaml.

Gopkg.lock

Gopkg.toml

...github.com/cortexproject/cortex/pkg/ring/consul_client.go

vendor/github.com/cortexproject/cortex/pkg/ring/kvstore.go

...or/github.com/cortexproject/cortex/pkg/ring/lifecycler.go

vendor/github.com/cortexproject/cortex/pkg/ring/ring.go

...r/github.com/cortexproject/cortex/pkg/util/flagext/day.go

...hub.com/cortexproject/cortex/pkg/util/flagext/register.go

...thub.com/cortexproject/cortex/pkg/util/flagext/strings.go

...r/github.com/cortexproject/cortex/pkg/util/flagext/url.go

vendor/github.com/cortexproject/cortex/pkg/util/net.go

vendor/github.com/prometheus/common/promlog/log.go