connectcore-demo-example: fix signal handling for DEY-4.0

With the update to DEY-4.0, the signal handling in the "demoserver.py" Python script
stopped working. The call to "event.wait()" caused the application to stop receiving
signals. This commit fixes the issue by replacing the event lock mechanism with the
"signal.sigwait()" call, which stops the thread execution until any specified signal
is received.

Signed-off-by: David Escalona <david.escalona@digi.com>

connectcore-demo-example/demoserver.py

@@ -31,7 +31,7 @@ import subprocess
 
 from logging.handlers import SysLogHandler
 from subprocess import call, TimeoutExpired
-from threading import Thread, Event
+from threading import Thread
 
 
 # Constants.
@@ -54,7 +54,6 @@ NOT_AVAILABLE = "N/A"
 
 # Variables.
 log = logging.getLogger(APP_NAME)
-stop_event = Event()
 last_cpu_work = 0
 last_cpu_total = 0
 led_status = {}
@@ -1109,8 +1108,6 @@ def signal_handler(signal_number, _frame):
         _frame: Current stack frame.
     """
     log.debug("Signal received %d", signal_number)
-    if signal_number in (signal.SIGTERM, signal.SIGINT):
-        stop_event.set()
 
 
 def main():
@@ -1146,7 +1143,8 @@ def main():
     server_thread.deamon = True
     server_thread.start()
 
-    stop_event.wait()
+    # Wait for termination/interrupt signal.
+    signal.sigwait([signal.SIGTERM, signal.SIGINT])
 
     server.shutdown()
     server.server_close()