[CONJ-583] Additional to ensure connection state when using intermedi…

…ate proxy.

If a failover occurs during this internal queries, and there is some intermediate proxy that doesn't do is the job, even writing to socket doesn't permit to ensure socket state, leaving the driver hanging indefinitely.
Socket timeout is set for internal connection queries

src/main/java/org/mariadb/jdbc/internal/protocol/AbstractConnectProtocol.java

@@ -431,6 +431,7 @@ public void connect() throws SQLException {
     private void connect(String host, int port) throws SQLException, IOException {
         try {
             socket = Utils.createSocket(urlParser, host);
+            if (options.socketTimeout != null) socket.setSoTimeout(options.socketTimeout);
 
             initializeSocketOption();
 
@@ -492,8 +493,6 @@ private void connect(String host, int port) throws SQLException, IOException {
                 loadCalendar(globalInfo.getTimeZone(), globalInfo.getSystemTimeZone());
             }
 
-            if (options.socketTimeout != null) socket.setSoTimeout(options.socketTimeout);
-
             reader.setServerThreadId(this.serverThreadId, isMasterConnection());
             writer.setServerThreadId(this.serverThreadId, isMasterConnection());
 
@@ -647,6 +646,10 @@ private void requestSessionDataWithShow(Map<String, String> serverData) throws S
                 }
                 serverData.put(resultSet.getString(1), resultSet.getString(2));
             }
+            if (serverData.size() < 4) {
+                throw ExceptionMapper.connException("could not load system variables. socket connected: " + socket.isConnected());
+            }
+
         } catch (SQLException sqlException) {
             throw ExceptionMapper.connException("could not load system variables", sqlException);
         }