Description of problem:
GET /api/hosts/:id shows errata_counts as integer if errata count > 0 and shows as null instead of 0 otherwise.

> GET https://sat6.com/api/v2/hosts/37
> {
> "id":37,
> ...
> "content_facet_attributes": {
>   "errata_counts": {
>     "security": 1,
>     "bugfix": null,
>     "enhancement": null,	
>     "total": 1

Version-Release number of selected component (if applicable):
Sat 6.3 Snap 11:
* satellite-6.3.0-16.0.beta.el7sat.noarch
* katello-3.4.4-2.el7sat.noarch
* foreman-1.15.3-1.el7sat.noarch

How reproducible:
Always

Steps to Reproduce:
To see only null values, omit steps 2 and 3.

1. Create and register content host
2. Add and synchronize repository with available errata
3. Install on the content host package that has applicable errata in the repository.
4. Check errata counts via GET /api/hosts/:id 

Actual results:
Errata count is integer if it is not zero and null oterwise.
On UI it is displayed as 0.

Expected results:
errata_counts field should contain 0.

Additional info: