[fix][broker] Create "standalone" cluster when starting standalone server

[massakam]

Motivation

Up to version 2.10.0, we could create any tenant as soon as we started the standalone server. However, the current master cannot do that.

$ ./bin/pulsar-admin tenants create foo

2022-05-13T13:33:21,852+0900 [AsyncHttpClient-7-1] WARN  org.apache.pulsar.client.admin.internal.BaseResource - [http://localhost:8080/admin/v2/tenants/foo] Failed to perform http put request: javax.ws.rs.ClientErrorException: HTTP 412 Clusters can not be empty
Clusters can not be empty

Reason: Clusters can not be empty

$ ./bin/pulsar-admin tenants create -c standalone foo

2022-05-13T13:33:37,011+0900 [AsyncHttpClient-7-1] WARN  org.apache.pulsar.client.admin.internal.BaseResource - [http://localhost:8080/admin/v2/tenants/foo] Failed to perform http put request: javax.ws.rs.ClientErrorException: HTTP 412 Clusters do not exist
Clusters do not exist

Reason: Clusters do not exist

Modifications

The reason why tenant creation fails is that the "standalone" cluster does not actually exist.

$ grep 'clusterName' conf/standalone.conf

clusterName=standalone

$ ./bin/pulsar-admin clusters get standalone

Cluster does not exist

Reason: Cluster does not exist

The process of creating this cluster has been removed in #15186, but it seems that there is no need to remove it. So, I added the process of creating the "standalone" cluster again.

Verifying this change

• Make sure that the change passes the CI checks.

Documentation

• no-need-doc

[merlimat]

@massakam The CPP tests are failing because the script is creating the standalone cluster again:

2022-05-13T10:28:38,588+0000 [AsyncHttpClient-7-1] WARN  org.apache.pulsar.client.admin.internal.BaseResource - [https://localhost:8443/admin/v2/clusters/standalone] Failed to perform http put request: javax.ws.rs.ClientErrorException: HTTP 409 Cluster already exists
[42](https://github.com/apache/pulsar/runs/6420579337?check_suite_focus=true#step:11:42)
Cluster already exists
[43](https://github.com/apache/pulsar/runs/6420579337?check_suite_focus=true#step:11:43)

[codelipenghui]

/pulsarbot run-failure-checks

[massakam]

@massakam The CPP tests are failing because the script is creating the standalone cluster again:

Fixed the script to create the standalone cluster only if it doesn't exist.