Partial revert of "Correctly close the NonBlockingReader to shutdown …

…the reading thread", fixes #167

This partially reverts commit b94e9b9.

terminal/src/main/java/org/jline/terminal/impl/PosixSysTerminal.java

@@ -93,6 +93,7 @@ public void close() throws IOException {
             Signals.unregister(entry.getKey().name(), entry.getValue());
         }
         super.close();
-        reader.close();
+        // Do not call reader.close()
+        reader.shutdown();
     }
 }