cli/command/container: stats: make stripping "/" prefix deterministic

This code was assuming the API always returns container names with
a "/" prefix. While this is currently correct, we may at some point
stop doing so.

This patch changes the code to only trim "/" as prefix and not any
other character.

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

Author: thaJeztah

cli/command/container/formatter_stats.go

@@ -2,6 +2,7 @@ package container
 
 import (
 	"strconv"
+	"strings"
 	"sync"
 
 	"github.com/docker/cli/cli/command/formatter"
@@ -167,9 +168,9 @@ func (c *statsContext) Container() string {
 }
 
 func (c *statsContext) Name() string {
-	// TODO(thaJeztah): make this explicitly trim the "/" prefix, not just any char.
-	if len(c.s.Name) > 1 {
-		return c.s.Name[1:]
+	// Trim the "/" prefix (if present).
+	if name := strings.TrimPrefix(c.s.Name, "/"); name != "" {
+		return name
 	}
 	return noValue
 }