autotest: fix possible hlrauc race condition

The AuthCenter will now wait for the RX thread to start before
continuing with the test.

Also removed the non blocking option and fixed the loop to
handle a blocking recvfrom call.

autotests/util/hlrauc.py

@@ -14,28 +14,29 @@ class AuthCenter:
     def __init__(self, sock_path, config_file):
         self._read_config(config_file)
         self._socket = socket.socket(socket.AF_UNIX, socket.SOCK_DGRAM)
-        self._socket.setblocking(0)
         if os.path.exists(sock_path):
             os.unlink(sock_path)
         self._socket.bind(sock_path)
 
         self._rxhandle = threading.Thread(target=self._rx_thread)
-        self._rxhandle.shutdown = False
+        self._rxhandle.ready = threading.Event()
         self._rxhandle.start()
 
+        # wait for rx thread to start
+        self._rxhandle.ready.wait()
+
     def _rx_thread(self):
+        self._rxhandle.ready.set()
         while (True):
-            if self._rxhandle.shutdown == True:
-                break
             try:
                 data, addr = self._socket.recvfrom(1000)
                 data = data.decode('ascii')
                 resp = self._process_data(data)
-            except BlockingIOError:
-                continue
+            except OSError:
+                break
             except:
                 print("Exception:", sys.exc_info()[0])
-                continue
+                break
             if resp:
                 self._socket.sendto(bytearray(resp, 'UTF-8'), addr)
 
@@ -235,9 +236,9 @@ class AuthCenter:
         '''
             Stop the Authentication server and close the socket
         '''
-        self._rxhandle.shutdown = True
-        self._rxhandle.join()
+        self._socket.shutdown(socket.SHUT_RDWR)
         self._socket.close()
+        self._rxhandle.join()
 
 if __name__ == '__main__':
     '''