ISSUE-2736: bookies hosts by metrics grow exponentially.

[sijie]

Original Issue: apache#2736

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BUG REPORT
There are many, many, many Prometheus Metrics names.

Describe the bug

^(bookkeeper_client_per_channel_bookie_client|bookkeeper_server_BookieHighPriorityThread|replication_bookkeeper_client_per_channel_bookie_client)_hostnames_port_.*

bookies hosts by metrics grow exponentially.

To Reproduce

Steps to reproduce the behavior:

1. Go to '...'
2. Click on '....'
3. Scroll down to '....'
4. See error

Expected behavior
Prometheus OOM (200Gbyte)

Screenshots

Additional context

Add any other context about the problem here.