Make MetricsServer.Listen blocking

Signed-off-by: Max Brunsfeld <mbrunsfeld@pivotallabs.com>
Remove metrics server

It is now its own repo: runtime-metrics-server

Signed-off-by: Max Brunsfeld <mbrunsfeld@pivotallabs.com>
Signed-off-by: Alex Suraci <asuraci@pivotallabs.com>