Fixed it by installing dgraph without system.d and creating the systemd service files manually:
Create service for alpha: /etc/systemd/system/dgraph-alpha.service:
[Unit]
Description=dgraph.io Alpha instance
Wants=network.target
After=network.target
Requires=dgraph-zero.service
[Service]
Type=simple
WorkingDirectory=/var/lib/dgraph
ExecStart=dgraph alpha -p /var/lib/dgraph/p -w /var/lib/dgraph/w
Restart=on-failure
StandardOutput=journal
StandardError=journal
User=dgraph
Group=dgraph
[Install]
WantedBy=multi-user.target
Create file for zero: /etc/systemd/system/dgraph-zero.service:
[Unit]
Description=dgraph.io Zero instance
Wants=network.target
After=network.target
[Service]
Type=simple
WorkingDirectory=/var/lib/dgraph
ExecStart=dgraph zero --wal /var/lib/dgraph/zw
Restart=on-failure
StandardOutput=journal
StandardError=journal
User=dgraph
Group=dgraph
[Install]
WantedBy=multi-user.target
RequiredBy=dgraph-alpha.service