[release-1.14] Stop previous remote cluster when updating secret

[istio-testing]

Manual cherrypick required.

#39367 failed to apply on top of branch "release-1.14":

Applying: Cleanup previous remote cluster when updating secret
Using index info to reconstruct a base tree...
M	pkg/kube/multicluster/secretcontroller.go
Falling back to patching base and 3-way merge...
Auto-merging pkg/kube/multicluster/secretcontroller.go
CONFLICT (content): Merge conflict in pkg/kube/multicluster/secretcontroller.go
error: Failed to merge in the changes.
hint: Use 'git am --show-current-patch=diff' to see the failed patch
Patch failed at 0001 Cleanup previous remote cluster when updating secret
When you have resolved this problem, run "git am --continue".
If you prefer to skip this patch, run "git am --skip" instead.
To restore the original branch and stop patching, run "git am --abort".

[hzxuzhonghu]

duplicate