BUG/MINOR: add missing field when parsing the `balance` field #556

Job	Run time
generate-models	1m 2s
HAProxy check commit message	0s
generate-specification	47s
license-check	15s
Build	23s
lint-spec	6s
go mod tidy	11s
golangci-lint	50s
Tests	2m 37s
e2e on HAProxy (2.1)	45s
e2e on HAProxy (2.2)	44s
e2e on HAProxy (2.3)	46s
e2e on HAProxy (2.4)	42s
e2e on HAProxy (2.5)	41s
e2e on HAProxy (2.6)	40s
e2e on HAProxy (2.7)	43s
e2e on HAProxy (2.8)	40s
	11m 52s

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