If the formula was ran on a system that reported an os_family that
wasn't one of "Debian", "RedHat", "Arch", "Suse" then the map.jinja
template would fail to render with "'NoneType' is not iterable.
This occurs because grains.filter_by will return None when it fails
match the grain to the input dictionary. The value is then blindly
passed into a dict.update() which causes the failure.
In this patch we ensure that the default values, as defined in
defaults.yaml, are always applied when grain matching fails.
```bash
firewalld-formula$ yamllint -s .
./pillar.example
2:1 warning missing document start "---" (document-start)
3:12 warning truthy value should be one of [false, true] (truthy)
12:13 warning truthy value should be one of [false, true] (truthy)
15:89 error line too long (108 > 88 characters) (line-length)
19:13 warning truthy value should be one of [false, true] (truthy)
30:89 error line too long (363 > 88 characters) (line-length)
96:89 error line too long (170 > 88 characters) (line-length)
108:15 error wrong indentation: expected 12 but found 14 (indentation)
115:13 error empty value in block mapping (empty-values)
116:2 error syntax error: found character '%' that cannot start any token
152:89 error line too long (112 > 88 characters) (line-length)
./firewalld/defaults.yaml
3:1 warning missing document start "---" (document-start)
```
