bump locket
bump locket

[finishes #152133318]

Submodule src/code.cloudfoundry.org/locket e37a509c..5e4fd298:
  > rename ticker -> clock
  > run the request metrics notifier runner and add an integration test

cloudfoundry-incubator/diego-release,cloudfoundry-incubator/diego-release,cloudfoundry-incubator/diego-release,cloudfoundry-incubator/diego-release