Add ignore broadcast tables when unregister storage unit #2519

Job	Run time
Detect Changed Files	10s
Import Global Environment / init-environment	5s
E2E - transaction on mysql:5.7	6m 21s
E2E - transaction on postgres:12-alpine	8m 11s
E2E - transaction on enmotech/opengauss:2.1.0	6m 23s
E2E - pipeline on mysql:5.7	13m 36s
E2E - pipeline on postgres:12-alpine	12m 15s
E2E - pipeline on enmotech/opengauss:2.1.0	15m 50s
E2E - showprocesslist on mysql:5.7	6m 28s
	1h 9m 19s

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