Remove superfluous reptition from usingdocker.md

Clarify wording about default docker ps options

Fix typo in dockerlinks.md

Docker-DCO-1.1-Signed-off-by: Paul Weaver <pauweave@cisco.com> (github: ch3pjw)
Merge pull request #6712 from SvenDowideit/pr_out_remove_superfluous_reptition_from_usingdocker_md

Remove superfluous reptition from usingdocker.md