[2.x] Fix CI

[dhmlau]

Description

Fix CI for 2.x branch in order for the juggler 2.x branch CI to pass.

Changes port back from master:

• increase UV_THREADPOOL_SIZE

Related issues

connect to https://github.com/strongloop/loopback-datasource-juggler/pull/1342

• None

Checklist

• [ ] New tests added or existing tests modified to cover all changes
• [ ] Code conforms with the style guide

[loay]

@slnode test please

[loay]

@slnode test please