[testing] Ensure run_prometheus.sh uses a writeable storage path (#3662)

Co-authored-by: Maru Newby <maru.newby@avalabs.org>

Author: marun

scripts/run_prometheus.sh

@@ -115,7 +115,7 @@ echo "Wrote configuration to ${CONFIG_PATH}"
 
 echo "Starting prometheus..."
 cd "${PROMETHEUS_WORKING_DIR}"
-nohup "${CMD}" --config.file=prometheus.yaml --web.listen-address=localhost:0 --enable-feature=agent > prometheus.log 2>&1 &
+nohup "${CMD}" --config.file=prometheus.yaml --storage.agent.path=./data --web.listen-address=localhost:0 --enable-feature=agent > prometheus.log 2>&1 &
 echo $! > "${PIDFILE}"
 echo "prometheus started with pid $(cat "${PIDFILE}")"
 # shellcheck disable=SC2016