Update hack/dind to match the rest of our scripts

No functional changes here, just coding style and maintainability.

Docker-DCO-1.1-Signed-off-by: Andrew Page <admwiggin@gmail.com> (github: tianon)
Month devpts before mounting subdirs

Docker-DCO-1.1-Signed-off-by: Guillaume J. Charmes <guillaume@charmes.net> (github: creack)
Merge pull request #5565 from creack/fix_devpts

Month devpts before mounting subdirs
Merge pull request #5462 from tianon/hack-dind-style

Update hack/dind to match the rest of our scripts
Fix docker man page to reference selinux-enable flag

Docker-DCO-1.1-Signed-off-by: Daniel Walsh <dwalsh@redhat.com> (github: rhatdan)