devops: make sure cron has necessary PATH

browser_patches/tools/cronjob.sh

@@ -23,6 +23,10 @@ if [[ (-z $AZ_ACCOUNT_KEY) || (-z $AZ_ACCOUNT_NAME) ]]; then
   exit 1
 fi
 
+if ! which az >/dev/null; then
+  echo "ERROR: az is not found in PATH"
+  exit 1
+fi
 
 BROWSER_NAME=""
 if [[ ("$1" == "firefox") || ("$1" == "firefox/") ]]; then