webhook: fix validateQuotaTopology for root quota #7222

Job	Run time
golangci-lint	56s
unit-tests(Check Go modules)	31s
unit-tests(Check manifests)	39s
unit-tests(Check auto-generated codes)	4m 27s
unit-tests(Verify gofmt)	49s
unit-tests(Verify govet)	49s
unit-tests(Run Go build)	1m 24s
unit-tests(Run Go test)	3m 14s
build-and-push (koordlet)	3m 50s
build-and-push (koord-manager)	2m 21s
build-and-push (koord-scheduler)	2m 51s
build-and-push (koord-descheduler)	2m 39s
	24m 30s

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