fix #4530 (comment)

Author: Neilpang

acme.sh

@@ -2235,9 +2235,13 @@ _send_signed_request() {
         if [ -z "$_sleep_overload_retry_sec" ]; then
           _sleep_overload_retry_sec=5
         fi
-        _info "It seems the CA server is currently overloaded, let's wait and retry. Sleeping $_sleep_overload_retry_sec seconds."
-        _sleep $_sleep_overload_retry_sec
-        continue
+        if [ $_sleep_overload_retry_sec -le 600 ]; then
+          _info "It seems the CA server is currently overloaded, let's wait and retry. Sleeping $_sleep_overload_retry_sec seconds."
+          _sleep $_sleep_overload_retry_sec
+          continue
+        else
+          _info "The retryafter=$_retryafter is too large > 600, not retry anymore."
+        fi
       fi
       if _contains "$_body" "JWS has invalid anti-replay nonce" || _contains "$_body" "JWS has an invalid anti-replay nonce"; then
         _info "It seems the CA server is busy now, let's wait and retry. Sleeping $_sleep_retry_sec seconds."