Change UNKNOWN_CODE_PLEASE_REPORT to identify uknown code

Changes UNKNOWN_CODE_PLEASE_REPORT to include packet.errno in it.

This makes it easier to identify hat the code is even if the code is not yet supported:

```
(node:1) UnhandledPromiseRejectionWarning: Error: UNKNOWN_CODE_PLEASE_REPORT: Query execution was interrupted, query_timeout exceeded
```

lib/protocol/sequences/Sequence.js

@@ -43,7 +43,7 @@ Sequence.prototype.hasErrorHandler = function() {
 };
 
 Sequence.prototype._packetToError = function(packet) {
-  var code = ErrorConstants[packet.errno] || 'UNKNOWN_CODE_PLEASE_REPORT';
+  var code = ErrorConstants[packet.errno] || 'UNKNOWN_CODE_PLEASE_REPORT: ' + packet.errno;
   var err  = new Error(code + ': ' + packet.message);
   err.code = code;
   err.errno = packet.errno;