fix: update outdated loadgen env variable in sandboxctl (#807)
fix: update outdated loadgen env variable in sandboxctl (#807)

* fix: update outdated loadgen env variable in sandboxctl

* fix: authenticate loadgen before restarting loadgen
GoogleCloudPlatform/cloud-ops-sandbox,GoogleCloudPlatform/cloud-ops-sandbox,GoogleCloudPlatform/cloud-ops-sandbox,GoogleCloudPlatform/cloud-ops-sandbox,GoogleCloudPlatform/cloud-ops-sandbox,GoogleCloudPlatform/cloud-ops-sandbox,GoogleCloudPlatform/cloud-ops-sandbox