Allow overriding log in plugins/audit

[juneidy]

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Feature Request

Use Case

So the change in 528ecbc means that whatever log I passed into auditLogger is not prioritised over the log from createServer.

I would imagine that whatever new log passed to auditLogger should take precedence.

Example API

const server = restify.createServer({ log: loggerA , ... });
server.on('after', restify.plugins.auditLogger({ log: loggerB, ... }));

I would expect loggerB would be used instead of loggerA.

Are you willing and able to implement this?

I can quickly do the fix, but not sure about the tests.