bump auction gunk

Submodule src/github.com/cloudfoundry-incubator/auction 8fd6168..31931a3:
  > Use Close() instead of Disconnect()
Submodule src/github.com/cloudfoundry/gunk 8d0c836..4033c30:
  > Replace Disconnect() with Close()

Signed-off-by: Johannes Petzold <jpetzold@pivotal.io>