[bugfix] [RHEL/7] Version #2 of service_disabled & service_enabled (unix:file_test based) template for systemd

This patchset updates the original version it to be able to properly handle also cases, when service is masked or enabled-runtime.

For service_disabled template - <b> service is considered to be disabled when: </b>
&nbsp;  * corresponding RPM isn't installed OR,
&nbsp;  * particular service got masked OR,
&nbsp;  * particular service is disabled on boot AND not enabled at runtime.

For testing this template is applied against abrtd service (service_abrtd_disabled check).

For service enabled template - <b> service is considered to be enabled when: </b>
&nbsp;  * corresponding RPM is installed AND,
&nbsp;  * service in question is not masked AND,
&nbsp;  * service in question is enabled on boot time

For testing this template has been applied against iptables service (service_iptables_enabled check).

Tested on RHEL-7 & works as expected (AFAICT).

Please review.

Thank you, Jan.