Add a test for mount.GetMounts

Because mount.parseInfoFile is only available on Linux

Docker-DCO-1.1-Signed-off-by: Kato Kazuyoshi <kato.kazuyoshi@gmail.com> (github: kzys)
FreeBSD's nullfs doesn't support file mount

FreeBSD doesn't have "bind" mount, but nullfs might be a similar feature.
However nullfs can mount only directories.

Docker-DCO-1.1-Signed-off-by: Kato Kazuyoshi <kato.kazuyoshi@gmail.com> (github: kzys)
Support FreeBSD on pkg/mount

Docker-DCO-1.1-Signed-off-by: Kato Kazuyoshi <kato.kazuyoshi@gmail.com> (github: kzys)
Update fedora.md

Docker-DCO-1.1-Signed-off-by: Alexander Shopov <ash@kambanaria.org> (github: alshopov)

Squashed by

Docker-DCO-1.1-Signed-off-by: SvenDowideit <SvenDowideit@home.org.au> (github: SvenDowideit)

replaces #6478

Docker-DCO-1.1-Signed-off-by: Alexander Shopov <ash@kambanaria.org> (github: )
Remove old tag format

Docker-DCO-1.1-Signed-off-by: Victor Vieux <vieux@docker.com> (github: vieux)
Fix header and about Docker links
Fix typo in the docs.

Fix a minor typographical error inside `run.md`.
Merge pull request #6599 from SvenDowideit/6478-update-fedora

Update fedora.md
Merge pull request #6620 from vieux/deprecate_tag_args

Remove old tag format
Merge pull request #4812 from kzys/freebsd-mount

FreeBSD support on pkg/mount
Merge pull request #6623 from rogaha/fix_header_links

Fix header and About Docker links
Merge pull request #6624 from jezenielzapanta/patch-1

Fix typo in the docs.