* Probe Huawei LTE API for device support on SSDP match
More or less as expected, the loosening of SSDP/UPnP data matches done
in #81643 started to yield false positives, as in #85402.
Coming up with robust matches solely based on the SSDP/UPnP data still
does not seem possible, so keep the matches as loose as they were made,
but additionally invoke a probe request on the API to determine if the
device looks like a supported one.
* Probe only after unique id checks
Prevents throwaway probes for discoveries already in progress.
* Fix SSDP result URL test, add missing assert on it
c625051665