[Pulsar admin] Can not get leader broker in non-leader brokers.

[zhanghaou]

Describe the bug
I can use admin cmd to get the leader broker in leader broker, but can not get the info from non-leader broker.

To Reproduce

1. enter non-leader broker
2. run ' pulsar-admin brokers leader-broker'
3. output:

Couldn't find leader broker

Reason: Couldn't find leader broker

link PR: #9799

[zhanghaou]

@linlinnn @codelipenghui Please take a look and check, thanks.

[Demogorgon314]

I will try to fix it.