Add fish shell completions from https://github.com/barnybug/docker-fish-completion.

Docker-DCO-1.1-Signed-off-by: Barnaby Gray <barnaby@pickle.me.uk> (github: barnybug)
mkdir /dev before doing mknod

Docker-DCO-1.1-Signed-off-by: Lewis Peckover <lew@lew.io> (github: lewispeckover)
Merge pull request #4411 from lewispeckover/fix_mkimage-yum_mknod

Add "mkdir /dev" before doing mknod in mkimage-yum
Merge pull request #4399 from barnybug/fish-completions

Add fish shell completions from github.com/barnybug/docker-fish-completion