bump locket
bump locket

[finishes #148145077]

Submodule src/code.cloudfoundry.org/locket dd53eabb..8fc918cd:
  > panic on config file errors
  > rename locket_test.go -> main_test.go

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