When connection is non-existential, continue to parse parameters.

[srh]

Closing main repo PR rethinkdb/rethinkdb#6156

It references the bug report rethinkdb/rethinkdb#5453 .

I suppose the driver could have this fix.

Describe the bug
A clear and concise description of what the bug is.

To Reproduce
Steps to reproduce the behavior:

1. TODO

Expected behavior
A clear and concise description of what you expected to happen.

Screenshots
If applicable, add screenshots to help explain your problem.

System info

• OS: [e.g. macOS Mojave 10.14.3]
• RethinkDB Version: [e.g. 2.4.0]

Additional context
Add any other context about the problem here.