added logic to wait for backup host to come back online before trying carp sync

opnsense-carp-dhcp.php

@@ -182,6 +182,16 @@ sleep(30);
 
 # try to sync carp settings to backup node/router
 printf("Starting the CARP Sync. \n");
+printf("Trying to ping sync host, %s. \n", $syncIP);
+while (true) {
+    exec("ping -c 4 " . $syncIP, $output, $result);
+    if ($result == 0) {
+        printf("Ping is successful. \n");
+        break;
+    } else {
+        printf("Ping unsuccessful. \n");
+    }
+}
 $syncStatus = trim(shell_exec('configctl system ha_reconfigure_backup'));
 printf("CARP Sync Status: %s. \n", $syncStatus);
 printf("finished the CARP Sync. \n");