Flaky-test: AdminApiTransactionMultiBrokerTest.setup

https://github.com/apache/pulsar/runs/7647562319?check_suite_focus=true
```
Error: Tests run: 2, Failures: 1, Errors: 0, Skipped: 1, Time elapsed: 100.773 s <<< FAILURE! - in org.apache.pulsar.broker.admin.v3.AdminApiTransactionMultiBrokerTest
Error: setup(org.apache.pulsar.broker.admin.v3.AdminApiTransactionMultiBrokerTest) Time elapsed: 98.777 s <<< FAILURE!
org.apache.pulsar.client.api.PulsarClientException: org.apache.pulsar.client.api.transaction.TransactionCoordinatorClientException: org.apache.pulsar.client.api.PulsarClientException$LookupException: {"errorMsg":"org.apache.pulsar.broker.PulsarServerException: Failed to acquire ownership for namespace bundle pulsar/system/0x00000000_0xffffffff","reqId":4590687001839393428, "remote":"localhost/127.0.0.1:46635", "local":"/127.0.0.1:55664"}
at org.apache.pulsar.client.impl.PulsarClientImpl.(PulsarClientImpl.java:225)
at org.apache.pulsar.client.impl.PulsarClientImpl.(PulsarClientImpl.java:154)
at org.apache.pulsar.client.impl.ClientBuilderImpl.build(ClientBuilderImpl.java:63)
at org.apache.pulsar.broker.transaction.TransactionTestBase.setUpBase(TransactionTestBase.java:146)
at org.apache.pulsar.broker.admin.v3.AdminApiTransactionMultiBrokerTest.setup(AdminApiTransactionMultiBrokerTest.java:41)
```

Start with the linked CI run and the setup path in TransactionTestBase.setUpBase and AdminApiTransactionMultiBrokerTest.setup. Rerun AdminApiTransactionMultiBrokerTest to confirm whether the namespace-bundle ownership failure reproduces. Done means the test setup completes reliably without the reported flaky failure.

Written by the indexing model from the issue text.