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/container_linux_test.go

@@ -333,9 +333,7 @@ func TestGetContainerState(t *testing.T) {
 }
 
 func TestGetContainerStateAfterUpdate(t *testing.T) {
-	var (
-		pid = os.Getpid()
-	)
+	pid := os.Getpid()
 	stat, err := system.Stat(pid)
 	if err != nil {
 		t.Fatal(err)