Fix the costTxnReq ignores nested RequestTxn issue

[ahrtr]

The costTxnReq ignores nested RequestTxn, so it may bypass backend quota check.

cc @fuweid @ivanvc @serathius

Without the second commit, the unit test reproduces the issue. After applying the patch (second commit), the test passes.

$ go test -run TestCostTxn -v
=== RUN   TestCostTxn
=== RUN   TestCostTxn/flat_put
=== RUN   TestCostTxn/nested_txn_put_in_success_branch_must_be_counted
    quota_test.go:77: 
        	Error Trace:	/Users/wachao/go/src/github.com/ahrtr/etcd/server/storage/quota_test.go:77
        	Error:      	Not equal: 
        	            	expected: 278
        	            	actual  : 0
        	Test:       	TestCostTxn/nested_txn_put_in_success_branch_must_be_counted
=== RUN   TestCostTxn/nested_txn_put_in_failure_branch_must_be_counted
    quota_test.go:77: 
        	Error Trace:	/Users/wachao/go/src/github.com/ahrtr/etcd/server/storage/quota_test.go:77
        	Error:      	Not equal: 
        	            	expected: 278
        	            	actual  : 0
        	Test:       	TestCostTxn/nested_txn_put_in_failure_branch_must_be_counted
--- FAIL: TestCostTxn (0.00s)
    --- PASS: TestCostTxn/flat_put (0.00s)
    --- FAIL: TestCostTxn/nested_txn_put_in_success_branch_must_be_counted (0.00s)
    --- FAIL: TestCostTxn/nested_txn_put_in_failure_branch_must_be_counted (0.00s)
FAIL
exit status 1
FAIL	go.etcd.io/etcd/server/v3/storage	0.407s

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 69.64%. Comparing base (81e09b0) to head (f1f8893).

Additional details and impacted files

Files with missing lines	Coverage Δ
server/storage/quota.go	67.10% <100.00%> (+0.43%)	⬆️

... and 27 files with indirect coverage changes

@@            Coverage Diff             @@
##             main   #22134      +/-   ##
==========================================
- Coverage   69.66%   69.64%   -0.03%     
==========================================
  Files         449      449              
  Lines       38177    38178       +1     
==========================================
- Hits        26597    26589       -8     
- Misses      10148    10155       +7     
- Partials     1432     1434       +2     

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[ivanvc]

Verified that the first commit breaks the tests. Thanks for the fix.

[kubernetes-prow]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: ahrtr, fuweid, ivanvc

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[ahrtr]

/cherry-pick release-3.7

[ahrtr]

/cherry-pick release-3.6

[k8s-infra-cherrypick-robot]

@ahrtr: new pull request created: #22139

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In response to this:

/cherry-pick release-3.7

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[k8s-infra-cherrypick-robot]

@ahrtr: new pull request created: #22140

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In response to this:

/cherry-pick release-3.6

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[ahrtr]

/cherry-pick release-3.5

[k8s-infra-cherrypick-robot]

@ahrtr: new pull request created: #22162

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In response to this:

/cherry-pick release-3.5

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