* Use native yaml for apache2 test
* Test removal of default modules with force
a2enmod on debian has `-f`, but not on SUSE (runs there without force).
Therefore don't test that option on SUSE.
The docs already specify that the option is intended for Debian systems
only.
This change corrects problems reported by the `yamllint` linter.
Since key duplication problems were removed in 4d48711, this commit
mainly fixes trailing spaces and extra empty lines at beginning/end of
files.
