cli: inspect: human readable volume output
Merge pull request #130 from spotify/dano/cli-inspect-volumes

cli: inspect: human readable volume output
agent: poll instead of waiting for container exit

We're doing this poll loop instead of docker.waitContainer() because we
saw the agent hang forever on waitContainer after the socket got into a
weird half-open state where the kernel (netstat/lsof) would only show
one end of the connection and restarting docker would not close the
socket.

¯\_(ツ)_/¯
remove unused class