This commit fixes how `pillar_roots` are generated and after this fix the
generated configuration does not contain any unnecessary new lines:
```yaml
pillar_roots:
base:
/srv/salt/dir1
dev:
/srv/salt/dir2
/srv/salt/dir3
locale:
/srv/salt/dir4
```
Before this commit the pillar_roots in `f_defaults.conf` for master would be
generated with a lot of empty lines in between directories, like this:
```yaml
pillar_roots:
base:
/srv/salt/dir1
dev:
/srv/salt/dir2
/srv/salt/dir3
local:
/srv/salt/dir4
```
The minion configuration is not affected and renders fine.