Update 66-mongodb.js

[dodois]

• Bugfix (non-breaking change which fixes an issue)
• [ x ] New feature (non-breaking change which adds functionality)

Proposed changes

Call done when the operation is complete

Checklist

• [ x ] I have read the contribution guidelines
• [ x ] For non-bugfix PRs, I have discussed this change on the forum/slack team.
• [ x ] I have run grunt to verify the unit tests pass
• [ ] I have added suitable unit tests to cover the new/changed functionality

[dceejay]

Hi @dodois

Useful update but as the done capability was added later - you need to check if it exists before calling it in case someone is running a very old version that doesn't pass it it.

eg see - https://github.com/node-red/node-red-nodes/blob/master/storage/mysql/68-mysql.js#L110
and
https://github.com/node-red/node-red-nodes/blob/master/storage/mysql/68-mysql.js#L110