[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.