Handle create=false when exact matching

[TaiWilkin]

Overview

When a facility list item is submitted with create=false and there is
no match found, a FacilityListItem is created with facility_id=None.
When another facility list item is submitted which exact matches that
FacilityListItem, an error was being thrown. Instead, we now filter
out FacilityListItems where the facility_id=None, allowing us to match
to the next best option (if one exists) or pass the FacilityListItem
on to the dedupe process.

Connects #1580

Testing Instructions

• Not on this branch, browse /api/docs/#!/facilities/facilities_create authorize with an API token
• Submit a facility with create=false twice. The second submission should result in ERROR_MATCHING

{
    "country": "Turkey",
    "name": "BAŞARI TEKSTİL",
    "address": "Merkezefendi"
}

• Switch to this branch and resubmit the facility. The submission should not throw an error.

Checklist

• fixup! commits have been squashed
• CI passes after rebase
• CHANGELOG.md updated with summary of features or fixes, following Keep a Changelog guidelines

[jwalgran]

Confirmed!

[TaiWilkin]

Thanks for reviewing!