Fix flaky TestOnQosPublishThenQOSComplete

[ohkinozomu]

How to reproduce:

$ go test -v -timeout 30s -run ^TestOnQosPublishThenQOSComplete$ github.com/wind-c/comqtt/v2/mqtt/hooks/storage/bolt -count=200

=== RUN   TestOnQosPublishThenQOSComplete
    bolt_test.go:437: 
        	Error Trace:	/home/runner/work/comqtt/comqtt/mqtt/hooks/storage/bolt/bolt_test.go:437
        	Error:      	Should be true
        	Test:       	TestOnQosPublishThenQOSComplete
--- FAIL: TestOnQosPublishThenQOSComplete (0.00s)