Fix errors detected by valgrind

I tried running chronyd in valgrind and the result was that there are four
places where memory is not initialized. A patch fixing the errors is in the
attachment.

ntp_core.c

@@ -300,6 +300,9 @@ create_instance(NTP_Remote_Address *remote_addr, NTP_Mode mode, SourceParameters
 
   result->tx_count = 0;
 
+  result->remote_orig.hi = 0;
+  result->remote_orig.lo = 0;
+
   result->score = 0;
 
   if (params->online) {