Don't wrap 'cp' help too soon.

Minor thing but docker cp --help was:
Copy files/folders from a PATH on the container to a HOSTDIR on the host
running the command. Use '-' to write the data
as a tar file to STDOUT.

This changes it to:
Copy files/folders from a PATH on the container to a HOSTDIR on the host
running the command. Use '-' to write the data as a tar file to STDOUT.

The \n made the output look funky.

Signed-off-by: Doug Davis <dug@us.ibm.com>