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/restored_process.go

@@ -11,9 +11,7 @@ import (
 )
 
 func newRestoredProcess(cmd *exec.Cmd, fds []string) (*restoredProcess, error) {
-	var (
-		err error
-	)
+	var err error
 	pid := cmd.Process.Pid
 	stat, err := system.Stat(pid)
 	if err != nil {