Data race in github.com/coreos/mantle/kola/tests/ignition.setupIgnitionConfig

[jlebon]

==================
WARNING: DATA RACE
Write at 0x00000467f460 by goroutine 89:
  github.com/coreos/mantle/kola/tests/ignition.setupIgnitionConfig()
      /root/containerbuild/mantle/kola/tests/ignition/mount.go:154 +0xc88
  github.com/coreos/mantle/kola/tests/ignition.testMountDisks()
      /root/containerbuild/mantle/kola/tests/ignition/mount.go:55 +0x49
  github.com/coreos/mantle/kola.runTest()
      /root/containerbuild/mantle/kola/harness.go:946 +0x821
  github.com/coreos/mantle/kola.runProvidedTests.func1()
      /root/containerbuild/mantle/kola/harness.go:461 +0x6f
  github.com/coreos/mantle/harness.tRunner()
      /root/containerbuild/mantle/harness/harness.go:441 +0x256

Previous write at 0x00000467f460 by goroutine 91:
  github.com/coreos/mantle/kola/tests/ignition.setupIgnitionConfig()
      /root/containerbuild/mantle/kola/tests/ignition/mount.go:154 +0xc88
  github.com/coreos/mantle/kola/tests/ignition.testMountPartitions()
      /root/containerbuild/mantle/kola/tests/ignition/mount.go:89 +0x49
  github.com/coreos/mantle/kola.runTest()
      /root/containerbuild/mantle/kola/harness.go:946 +0x821
  github.com/coreos/mantle/kola.runProvidedTests.func1()
      /root/containerbuild/mantle/kola/harness.go:461 +0x6f
  github.com/coreos/mantle/harness.tRunner()
      /root/containerbuild/mantle/harness/harness.go:441 +0x256

Goroutine 89 (running) created at:
  github.com/coreos/mantle/harness.(*H).Run()
      /root/containerbuild/mantle/harness/harness.go:479 +0x72c
  github.com/coreos/mantle/harness.(*Suite).runTests.func1()
      /root/containerbuild/mantle/harness/suite.go:289 +0x124
  github.com/coreos/mantle/harness.tRunner()
      /root/containerbuild/mantle/harness/harness.go:441 +0x256
  github.com/coreos/mantle/harness.(*Suite).runTests()
      /root/containerbuild/mantle/harness/suite.go:287 +0x311
  github.com/coreos/mantle/harness.(*Suite).Run()
      /root/containerbuild/mantle/harness/suite.go:274 +0x549
  github.com/coreos/mantle/kola.runProvidedTests()
      /root/containerbuild/mantle/kola/harness.go:467 +0x7ad
  github.com/coreos/mantle/kola.RunTests()
      /root/containerbuild/mantle/kola/harness.go:490 +0x2e4
  main.runRun()
      /root/containerbuild/mantle/cmd/kola/kola.go:188 +0x8e
  github.com/spf13/cobra.(*Command).execute()
      /root/containerbuild/mantle/vendor/github.com/spf13/cobra/command.go:840 +0x505
  github.com/spf13/cobra.(*Command).ExecuteC()
      /root/containerbuild/mantle/vendor/github.com/spf13/cobra/command.go:945 +0x492
  github.com/spf13/cobra.(*Command).Execute()
      /root/containerbuild/mantle/vendor/github.com/spf13/cobra/command.go:885 +0x215
  github.com/coreos/mantle/cli.Execute()
      /root/containerbuild/mantle/cli/cli.go:67 +0x220
  main.main()
      /root/containerbuild/mantle/cmd/kola/kola.go:130 +0x4a

Goroutine 91 (running) created at:
  github.com/coreos/mantle/harness.(*H).Run()
      /root/containerbuild/mantle/harness/harness.go:479 +0x72c
  github.com/coreos/mantle/harness.(*Suite).runTests.func1()
      /root/containerbuild/mantle/harness/suite.go:289 +0x124
  github.com/coreos/mantle/harness.tRunner()
      /root/containerbuild/mantle/harness/harness.go:441 +0x256
  github.com/coreos/mantle/harness.(*Suite).runTests()
      /root/containerbuild/mantle/harness/suite.go:287 +0x311
  github.com/coreos/mantle/harness.(*Suite).Run()
      /root/containerbuild/mantle/harness/suite.go:274 +0x549
  github.com/coreos/mantle/kola.runProvidedTests()
      /root/containerbuild/mantle/kola/harness.go:467 +0x7ad
  github.com/coreos/mantle/kola.RunTests()
      /root/containerbuild/mantle/kola/harness.go:490 +0x2e4
  main.runRun()
      /root/containerbuild/mantle/cmd/kola/kola.go:188 +0x8e
  github.com/spf13/cobra.(*Command).execute()
      /root/containerbuild/mantle/vendor/github.com/spf13/cobra/command.go:840 +0x505
  github.com/spf13/cobra.(*Command).ExecuteC()
      /root/containerbuild/mantle/vendor/github.com/spf13/cobra/command.go:945 +0x492
  github.com/spf13/cobra.(*Command).Execute()
      /root/containerbuild/mantle/vendor/github.com/spf13/cobra/command.go:885 +0x215
  github.com/coreos/mantle/cli.Execute()
      /root/containerbuild/mantle/cli/cli.go:67 +0x220
  main.main()
      /root/containerbuild/mantle/cmd/kola/kola.go:130 +0x4a
==================

Seen in CI of #2283.