--help option and help command should print to stdout not stderr

    --help and help are successful commands so output should not go to error.

    QE teams have requested this change, also users doing docker help | less
    or docker run --help | less would expect this to work.

    Usage statement should only be printed when the user asks for it.
    Errors should print error message and then suggest the docker COMMAND --help
    command to see usage information.

    The current behaviour causes the user to have to search for the error message
    and sometimes scrolls right off the screen.  For example a error on a
    "docker run" command is very difficult to diagnose.

    Finally erros should always exit with a non 0 exit code, if the user
    makes a CLI error.

    Docker-DCO-1.1-Signed-off-by: Dan Walsh <dwalsh@redhat.com> (github: rhatdan)

Docker-DCO-1.1-Signed-off-by: Dan Walsh <dwalsh@redhat.com> (github: rhatdan)
Remove TestUsage, since Usage will no longer be shown on failure to parse

Docker-DCO-1.1-Signed-off-by: Dan Walsh <dwalsh@redhat.com> (github: rhatdan)