Add new validate-dco and validate-gofmt bundlescripts for DCO and gofmt validation

Docker-DCO-1.1-Signed-off-by: Andrew Page <admwiggin@gmail.com> (github: tianon)
Remove the old Travis-specific files that are no longer necessary

Docker-DCO-1.1-Signed-off-by: Andrew Page <admwiggin@gmail.com> (github: tianon)
Merge pull request #5022 from tianon/make-validate

Add "make validate" for both local and CI gofmt and DCO verification