idf_monitor: fix the bug that idf_monitor not blocked when no log printed

Inspired by @no1seman, @negativekelvin and @pglen on Github. (In post oder)

Resolves https://github.com/espressif/esp-idf/issues/3884

tools/idf_monitor.py

@@ -490,7 +490,7 @@ class Monitor(object):
                     item = self.cmd_queue.get_nowait()
                 except queue.Empty:
                     try:
-                        item = self.event_queue.get(False, 0.001)
+                        item = self.event_queue.get(True, 0.03)
                     except queue.Empty:
                         continue