Bump etcd-metrics-server

[#78292566]

Bump cloudfoundry-incubator/etcd-metrics-server:
  Abhijit Hiremagalur:
     Remove Godeps; deps are vendored in diego-release ( Travis created: https://travis-ci.org/cloudfoundry-incubator/etcd-metrics-server/builds/35479371 )

Signed-off-by: Matthew Sykes <matthew.sykes@gmail.com>