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/console_linux.go

@@ -9,7 +9,7 @@ import (
 // mount initializes the console inside the rootfs mounting with the specified mount label
 // and applying the correct ownership of the console.
 func mountConsole(slavePath string) error {
-	oldMask := unix.Umask(0000)
+	oldMask := unix.Umask(0o000)
 	defer unix.Umask(oldMask)
 	f, err := os.Create("/dev/console")
 	if err != nil && !os.IsExist(err) {