update exporter conf for mongoDB and mysql

templates/systemd/prometheus-mongodb-exporter.service.j2

@@ -5,7 +5,7 @@ After=network.target
 [Service]
 Type=simple
 ExecStart=/usr/local/bin/prometheus-mongodb-exporter
-EnvironmentFile=/etc/mongodb-exporter.conf
+EnvironmentFile=/etc/default/prometheus-mongodb-exporter
 
 [Install]
 WantedBy=multi-user.target

templates/systemd/prometheus-postgres-exporter.service.j2

@@ -1,10 +1,12 @@
 [Unit]
 Description=Prometheus PostgreSQL Exporter
 After=network.target
- 
+
 [Service]
 Type=simple
+User={{ prometheus_postgres_exporter_user|default("postgres") }} 
 ExecStart=/usr/local/bin/prometheus-postgres-exporter
- 
+EnvironmentFile=/etc/default/prometheus-postgres-exporter
+
 [Install]
 WantedBy=multi-user.target