PMM-12913 add check-agent-setup script

build/scripts/utils/check-agent-setup.sh

@@ -0,0 +1,9 @@
+#!/bin/bash
+
+# This script checks if PMM Server has finished upgrading so pmm-agent can perform the `setup` command.
+# If PMM Server is not ready, the script will wait for 30 seconds and then exit with an error.
+
+if ! timeout 30 bash -c "until supervisorctl status pmm-update-perform-init | grep -q EXITED; do sleep 2; done"; then
+    echo "FATAL: failed to set up pmm-agent."
+    exit 1
+fi