Fixes #39196 - Render Puppet masterport setting

[jakduch]

Fixes #39196

The puppet.conf snippet currently renders a custom Puppet server port as port, which is not the Puppet agent setting used to contact Puppet Server. Render the value as masterport while continuing to omit the default port.

Testing prerequisites:

• None

Testing scenarios:

• Set puppet_server_port to 4443 and render puppet.conf. Verify masterport = 4443 is present and port = 4443 is absent.
• Set puppet_server_port to 8140 and verify masterport is omitted.

Verification:

• Targeted renderer tests pass on Ruby 3.3 with PostgreSQL 13.
• Full test:units passes: 5,648 tests and 14,085 assertions, with 0 failures and 0 errors.
• RuboCop reports no offenses in the added test.