LCOW: fix using wrong shell for healthchecks

As reported in docker/compose#6445, when deploying a Linux
container on Windows (LCOW), the daemon made the wrong assumption
when deciding which shell to use to execute the healthcheck, looking
at the host's platform instead of the container's platform.

This patch adds a check for the container's platform when deploying
on Windows, and sets the correct shell.

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

daemon/health.go

@@ -10,7 +10,6 @@ import (
 	"time"
 
 	"github.com/docker/docker/api/types"
-	containertypes "github.com/docker/docker/api/types/container"
 	"github.com/docker/docker/api/types/strslice"
 	"github.com/docker/docker/container"
 	"github.com/docker/docker/daemon/exec"
@@ -65,7 +64,7 @@ type cmdProbe struct {
 func (p *cmdProbe) run(ctx context.Context, d *Daemon, cntr *container.Container) (*types.HealthcheckResult, error) {
 	cmdSlice := strslice.StrSlice(cntr.Config.Healthcheck.Test)[1:]
 	if p.shell {
-		cmdSlice = append(getShell(cntr.Config), cmdSlice...)
+		cmdSlice = append(getShell(cntr), cmdSlice...)
 	}
 	entrypoint, args := d.getEntrypointAndArgs(strslice.StrSlice{}, cmdSlice)
 	execConfig := exec.NewConfig()
@@ -376,12 +375,15 @@ func min(x, y int) int {
 	return y
 }
 
-func getShell(config *containertypes.Config) []string {
-	if len(config.Shell) != 0 {
-		return config.Shell
+func getShell(cntr *container.Container) []string {
+	if len(cntr.Config.Shell) != 0 {
+		return cntr.Config.Shell
 	}
 	if runtime.GOOS != "windows" {
 		return []string{"/bin/sh", "-c"}
 	}
+	if cntr.OS != runtime.GOOS {
+		return []string{"/bin/sh", "-c"}
+	}
 	return []string{"cmd", "/S", "/C"}
 }