[fix][ml] Fix wrong configuration passed to managed ledger when deleting

[mattisonchao]

Motivation

#21093 Delete the topic policy before the managed ledger configuration building. It will pass the wrong managed ledger configuration to the backend and affect offloading etc.

Modifications

• Get managed ledger configuration before deleting topic policies.

Verifying this change

• Make sure that the change passes the CI checks.

Documentation

• doc
• doc-required
• doc-not-needed
• doc-complete

[codelipenghui]

Is it possible to add a test to avoid regressions?

[mattisonchao]

I am unsure at first glance. I think the test is challenging to add. I am considering whether it is worth to spend that time. :/

@codelipenghui, do you think this test is necessary? I mean the problem looks pretty straightforward.

[mattisonchao]

I will add the test to avoid regression. :)

[Technoboy-]

topicPoliciesFuture throw exception because race condition occurs in getManagedLedgerConfig.
Need to handle exception for topicPoliciesFuture