[backport 20.10] TestDaemonRestartKillContainers: Fix races

[vvoland]

• Cherrypick: TestDaemonRestartKillContainers: Fix races #45168

TestDaemonRestartKillContainers: Fix loop capture

TestDaemonRestartKillContainers test was always executing the last case (container created should not be restarted) because the iterated variables were not copied correctly.
Capture iterated values by value correctly.

StartWithLogFile: Fix d.cmd race

Use exec.Command created by this function instead of obtaining it from daemon struct. This prevents a race condition where daemon.Kill is called before the goroutine has the chance to call cmd.Wait.

Detected by -race:

WARNING: DATA RACE
Write at 0x00c00071c048 by goroutine 40:
  github.com/docker/docker/testutil/daemon.(*Daemon).Kill.func1()
      /go/src/github.com/docker/docker/testutil/daemon/daemon.go:497 +0x88
  runtime.deferreturn()
      /usr/local/go/src/runtime/panic.go:476 +0x32
  github.com/docker/docker/integration/container.TestDaemonRestartKillContainers.func1()
      /go/src/github.com/docker/docker/integration/container/restart_test.go:72 +0x31
  github.com/docker/docker/integration/container.TestDaemonRestartKillContainers.func3()
      /go/src/github.com/docker/docker/integration/container/restart_test.go:111 +0x6b8
  testing.tRunner()
      /usr/local/go/src/testing/testing.go:1576 +0x216
  testing.(*T).Run.func1()
      /usr/local/go/src/testing/testing.go:1629 +0x47

Previous read at 0x00c00071c048 by goroutine 50:
  github.com/docker/docker/testutil/daemon.(*Daemon).StartWithLogFile.func1()
      /go/src/github.com/docker/docker/testutil/daemon/daemon.go:413 +0x46

- How to verify it

make  BUILDFLAGS='-race'  TEST_FILTER='TestDaemonRestartKillContainers'  test-integration

- Description for the changelog

- A picture of a cute animal (not mandatory but encouraged)

[thaJeztah]

LGTM