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/config_linux_test.go

@@ -4,9 +4,7 @@ import (
 	"testing"
 )
 
-var (
-	HookNameList = []HookName{Prestart, CreateRuntime, CreateContainer, StartContainer, Poststart, Poststop}
-)
+var HookNameList = []HookName{Prestart, CreateRuntime, CreateContainer, StartContainer, Poststart, Poststop}
 
 func TestRemoveNamespace(t *testing.T) {
 	ns := Namespaces{