cli-plugins: PluginRunCommand: use cmd.Environ instead of os.Environ

Commit 5011759 implemented a fix that
caused the current environment to be discarded, using `os.Environ()`.
On Windows, `os.Environ()` may produce an incorrect value for `PWD`,
for which a new function was added in go1.19;

- https://tip.golang.org/doc/go1.19#osexecpkgosexec
- https://go-review.googlesource.com/c/go/+/401340

Replace the use of `os.Environ()` with `cmd.Environ()` to address that.

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>
(cherry picked from commit 5ccb484)
Signed-off-by: Paweł Gronowski <pawel.gronowski@docker.com>

cli-plugins/manager/manager.go

@@ -240,8 +240,7 @@ func PluginRunCommand(dockerCli command.Cli, name string, rootcmd *cobra.Command
 		cmd.Stdout = os.Stdout
 		cmd.Stderr = os.Stderr
 
-		cmd.Env = os.Environ()
-		cmd.Env = append(cmd.Env, ReexecEnvvar+"="+os.Args[0])
+		cmd.Env = append(cmd.Environ(), ReexecEnvvar+"="+os.Args[0])
 		cmd.Env = appendPluginResourceAttributesEnvvar(cmd.Env, rootcmd, plugin)
 
 		return cmd, nil