[FAB-18298] Default cluster cert and key (bp #2078)

[mergify]

This is an automated backport of pull request #2078 done by Mergify

Cherry-pick of d620ab3 has failed:

On branch mergify/bp/release-2.2/pr-2078
Your branch is up to date with 'origin/release-2.2'.

You are currently cherry-picking commit d620ab33e.
  (fix conflicts and run "git cherry-pick --continue")
  (use "git cherry-pick --abort" to cancel the cherry-pick operation)

Changes to be committed:

	modified:   integration/raft/cft_test.go
	modified:   orderer/common/server/main.go

Unmerged paths:
  (use "git add <file>..." to mark resolution)

	both modified:   orderer/common/server/main_test.go

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