feat: append additional configuration to deadline-worker systemd config during linux worker setup (#181)

Signed-off-by: Godot Bian <[email protected]>
Co-authored-by: Godot Bian <[email protected]>

Author: godobyte

Diff for: src/deadline_test_fixtures/deadline/worker.py

@@ -698,7 +698,7 @@ def configure_agent_user_environment(
         cmds.extend(
             [
                 "mkdir -p /etc/systemd/system/deadline-worker.service.d/",
-                'echo "[Service]" > /etc/systemd/system/deadline-worker.service.d/config.conf',
+                'echo "[Service]" >> /etc/systemd/system/deadline-worker.service.d/config.conf',
                 # Configure the region
                 f'echo "Environment=AWS_REGION={config.region}" >> /etc/systemd/system/deadline-worker.service.d/config.conf',
                 f'echo "Environment=AWS_DEFAULT_REGION={config.region}" >> /etc/systemd/system/deadline-worker.service.d/config.conf',