docker top: fix command when multiple arguments are supplied

Docker-DCO-1.1-Signed-off-by: Erik Hollensbe <github@hollensbe.org> (github: erikh)
Add a test for the multiple arguments passed to `docker top`

Docker-DCO-1.1-Signed-off-by: Erik Hollensbe <github@hollensbe.org> (github: erikh)
Merge pull request #7812 from erikh/fix_top

docker top: fix command when multiple arguments are supplied