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/cgroups/systemd/v1.go

@@ -238,7 +238,7 @@ func (m *legacyManager) joinCgroups(pid int) error {
 			}
 		default:
 			if path, ok := m.paths[name]; ok {
-				if err := os.MkdirAll(path, 0755); err != nil {
+				if err := os.MkdirAll(path, 0o755); err != nil {
 					return err
 				}
 				if err := cgroups.WriteCgroupProc(path, pid); err != nil {