[FIX] hw_drivers: Start iot_devices thread after registering it

This commit was originally part of a larger commit related to an
Ingenico double connection deadlock bugfix in V13, but in V14 most of
the related code has moved to enterprise. When a driver thread is
running, calling `disconnect` on it will delete it from iot_devices. If
the driver thread gets added to iot_devices in the Interface thread
after starting it, this means there is a tiny window of time where
`disconnect` could be called and the thread wouldn't be in iot_devices
yet, resulting in an exception. This change puts the driver thread in
iot_devices before starting it, avoiding that scenario and the need to
check in `disconnect` for that happening.

X-original-commit: 6c24d30c3910e67ed751327d1554e2e8cf5e958b

addons/hw_drivers/interface.py

@@ -51,8 +51,12 @@ class Interface(Thread, metaclass=InterfaceMetaClass):
                     _logger.info('Device %s is now connected', identifier)
                     d = driver(identifier, devices[identifier])
                     d.daemon = True
-                    d.start()
                     iot_devices[identifier] = d
+                    # Start the thread after creating the iot_devices entry so the
+                    # thread can assume the iot_devices entry will exist while it's
+                    # running, at least until the `disconnect` above gets triggered
+                    # when `removed` is not empty.
+                    d.start()
                     break
 
     def get_devices(self):