[Issue 12726] [broker] Fix deadlock in metadata-store callback thread for branch 2.9

[Jason918]

Fixes #12726 for branch 2.9

Motivation

See #12726

#12753 fixed this in master, but can not merged into branch 2.9.

Modifications

Use thenAcceptAsync instead to avoid dead lock on metadata thread.

Verifying this change

• Make sure that the change passes the CI checks.

This change is already covered by existing tests, such as org.apache.pulsar.broker.admin.PersistentTopicsTest

Does this pull request potentially affect one of the following parts:

If yes was chosen, please highlight the changes

• Dependencies (does it add or upgrade a dependency): (no)
• The public API: (no)
• The schema: (no)
• The default values of configurations: (no)
• The wire protocol: (no)
• The rest endpoints: (no)
• The admin cli options: (no)
• Anything that affects deployment: (no)

Documentation

Check the box below and label this PR (if you have committer privilege).

Need to update docs?

• no-need-doc
  Bug fix.

[Jason918]

@codelipenghui PTAL