pgrep command doesn't exist in the latest pmm docker image - workaround

Author: ptankov

e2e-tests/monitoring-2-0/run

@@ -32,8 +32,7 @@ else
 	retry 10 60 helm install monitoring --set imageTag=$IMAGE_PMM_SERVER_TAG --set imageRepo=$IMAGE_PMM_SERVER_REPO --set platform=$platform https://percona-charts.storage.googleapis.com/pmm-server-${PMM_SERVER_VER}.tgz
 fi
 sleep 20
-SERVICE="postgres"
-until kubectl_bin exec monitoring-0 -- bash -c "pgrep -x $SERVICE >/dev/null"; do
+until kubectl_bin exec monitoring-0 -- bash -c "ls -l /proc/*/exe 2>/dev/null| grep postgres >/dev/null"; do
 	echo "Retry $retry"
 	sleep 5
 	let retry+=1