Use gofumpt to format code

gofumpt (mvdan.cc/gofumpt) is a fork of gofmt with stricter rules.

Brought to you by

	git ls-files \*.go | grep -v ^vendor/ | xargs gofumpt -s -w

Looking at the diff, all these changes make sense.

Also, replace gofmt with gofumpt in golangci.yml.

Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>

libcontainer/configs/namespaces_unsupported.go

@@ -4,5 +4,4 @@ package configs
 
 // Namespace defines configuration for each namespace.  It specifies an
 // alternate path that is able to be joined via setns.
-type Namespace struct {
-}
+type Namespace struct{}