Check the correct stream if there is more data pending

The input stream might no longer be the raw socket, so we need to
query what's currently active. That wrapping stream might have its
own buffering and may have more data even if the socket is drained.

vncviewer/CConn.cxx

@@ -266,7 +266,7 @@ void CConn::socketEvent(FL_SOCKET fd, void *data)
        // Also check if we need to stop reading and terminate
        if (should_exit())
          break;
-    } while (cc->sock->inStream().checkNoWait(1));
+    } while (cc->getInStream()->checkNoWait(1));
   } catch (rdr::EndOfStream& e) {
     vlog.info("%s", e.str());
     exit_vncviewer();