Bump github.com/containers/storage from 1.15.8 to 1.16.0

Bumps [github.com/containers/storage](https://github.com/containers/storage) from 1.15.8 to 1.16.0.
- [Release notes](https://github.com/containers/storage/releases)
- [Changelog](https://github.com/containers/storage/blob/master/docs/containers-storage-changes.md)
- [Commits](https://github.com/containers/storage/compare/v1.15.8...v1.16.0)

Signed-off-by: dependabot-preview[bot] <support@dependabot.com>
Signed-off-by: Valentin Rothberg <rothberg@redhat.com>

vendor/github.com/mattn/go-shellwords/util_go15.go

@@ -1,29 +0,0 @@
-// +build !go1.6
-
-package shellwords
-
-import (
-	"os"
-	"os/exec"
-	"runtime"
-	"strings"
-)
-
-func shellRun(line, dir string) (string, error) {
-	var b []byte
-	var err error
-	var cmd *exec.Cmd
-	if runtime.GOOS == "windows" {
-		cmd = exec.Command(os.Getenv("COMSPEC"), "/c", line)
-	} else {
-		cmd = exec.Command(os.Getenv("SHELL"), "-c", line)
-	}
-	if dir != "" {
-		cmd.Dir = dir
-	}
-	b, err = cmd.Output()
-	if err != nil {
-		return "", err
-	}
-	return strings.TrimSpace(string(b)), nil
-}

vendor/github.com/mattn/go-shellwords/util_posix.go

@@ -1,4 +1,4 @@
-// +build !windows,go1.6
+// +build !windows
 
 package shellwords
 
@@ -10,7 +10,10 @@ import (
 )
 
 func shellRun(line, dir string) (string, error) {
-	shell := os.Getenv("SHELL")
+	var shell string
+	if shell = os.Getenv("SHELL"); shell == "" {
+		shell = "/bin/sh"
+	}
 	cmd := exec.Command(shell, "-c", line)
 	if dir != "" {
 		cmd.Dir = dir

vendor/github.com/mattn/go-shellwords/util_windows.go

@@ -1,4 +1,4 @@
-// +build windows,go1.6
+// +build windows
 
 package shellwords
 
@@ -10,7 +10,10 @@ import (
 )
 
 func shellRun(line, dir string) (string, error) {
-	shell := os.Getenv("COMSPEC")
+	var shell string
+	if shell = os.Getenv("COMSPEC"); shell == "" {
+		shell = "cmd"
+	}
 	cmd := exec.Command(shell, "/c", line)
 	if dir != "" {
 		cmd.Dir = dir