Fixed issue where the SimpleService stop_announce method would crash

[AlwinHughes]

I've noticed that calling the stop_announce method on the SimpleService class causes the program will crash.

The crash is caused by the stop_announce method re-constructing the instance so that when the announcer searches through it's list of services it is announcing it is unable to remove the service instance on this line:
https://github.com/afflux/pysomeip/blob/master/src/someip/sd.py#L1313

If you simple call the stop method of SimpleService this issue is not encountered by SD announcer won't stop announcing the service.
In in the toos/simpleservice.py file this is circumvented as the entire announcer is stopped before the SimpleService is stopped.

I've made an example of this here: https://github.com/AlwinHughes/pysomeip/blob/demo/tools/simpleservice.py. This demo will crash if it's run with the version of SimpleService that is on the current afflux/master but completes successfully with the changes in this PR.

My proposed solution is to store the service_instance when SimpleService start_announce is called. Then when stop_announce is called the correct instance can be passed to the announcer. This allows multiple SimpleServices to be announced by the same ServiceAnnouncer and each service to be offered/stopped independent of each other.

I'm new to contributing to open source projects so please let me know what you think or if I've missed anything.

[afflux]

Hi! Thanks a lot for your contribution. The original code is even more wrong than what you describe - in stop_announce, I'm passing a config.Service instead of the sd.ServiceInstance. Good catch! The CI will probably error, but that is not on you, I'll fix that in a bit.

[AlwinHughes]

Ahh OK yeah I missed that. I guess my explanation was also wrong as I though the python remove method worked by reference rather than value. Glad to be able to help.

[AlwinHughes]

Hey, just wondering if there's anything I can do to help get this merged?