Make use of %USERPROFILE% in cli help message

An earlier commit was causing docker windows CLI build to not to pick up
the shorthand form for home directory (`%USERPROFILE%`) shown in when
`docker --help` is executed.

Fixing that bug and making the if statement concise and clear.

Signed-off-by: Ahmet Alp Balkan <ahmetalpbalkan@gmail.com>