service: Add default Environment option

The Fedora service file now contains this directive to avoid systemd
complaining about unused variable in case the EnvironmentFile is empty
or does not exists. Defining empty variable should not hurt other
distros.

Signed-off-by: Jakub Jelen <jjelen@redhat.com>

Author: Jakuje

templates/sshd.service.j2

@@ -12,6 +12,7 @@ Documentation=man:sshd(8) man:sshd_config(5)
 
 [Service]
 Type=notify
+Environment={{ __sshd_environment_variable }}=
 {% if __sshd_environment_file is string %}
 EnvironmentFile={{ __sshd_environment_file_mandatory | ternary('', '-')}}{{ __sshd_environment_file }}
 {% elif __sshd_environment_file is iterable %}