Closing Bucket During Async Finally Block Causes Crash

This low-level error will crash the Node process, preventing handling of the exception.  I would assume it's related to something happening inside libcouchbase when disconnect is called during exception handling.

Windows Error Message (Node 8.9.4):
Assertion failed: handle->type == UV_PREPARE, file src\win\loop-watcher.c, line 120

Linux Error Message (Node 8.9.4 on Alpine Linux in Docker container):
Segmentation fault

Steps to Reproduce:

1. Download this repo: https://github.com/brantburnett/couchnode-error-repro
2. Run `npm install`
3. Run `npm test`

Docker Steps to Reproduce:

1. Download the same repo
2. Run `docker-compose up --build`