wispr: check service before stopping portal detection

Do not stop wispr unconditionally. Make sure that wispr matches service
before stopping it. Otherwise removal of unrelevant service may cancel
ongoing online check. For instance, this is the case for WiFi networks,
since their services share the same index equal to network device index.
So when unused WiFi services are removed, online check for active WiFi
service is canceled before completion and not rescheduled.
1 file changed