Update bin/bookkeeper script.

[MarvinCai]

Fixes https://github.com/apache/pulsar/issues/16904

Motivation

Allowing user to override default -Djava.net.preferIPv4Stack=true config to run bookie init command in ipv6 environment.

Verifying this change

• [x] Make sure that the change passes the CI checks.

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

• 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: (yes) Should be able to init bookkeeper cluster in ipv6 env using bin/bookkeeper shell initnewcluster

Documentation

Need to update docs?

• [x] doc-not-needed