add 100ms usleep to reduce request frequency

switchepp.php

@@ -1013,6 +1013,10 @@ function switchepp_AdminDomainsTabFields($params)
 
 function switchepp_Sync($params)
 {
+    /***
+     * [error] => Command failed; server closing connection. Too many requests per second! Timeout ms.: 47107
+     * using usleep to slow down request frequency
+    */
     usleep(100000);
     try {
         $client = switchepp_clientloginepp($params);      #Epp Connection