Fix test-case: do not import SSDP_PORT and SSDP_ADDR, but define.

IF for any reason, this would change, the test-case must reflect that.
Add some test-cases for upnp.core.msearch.
Rework code for test-cases for upnp-core-ssdp a bit.
Add a test-case for upnp.core.ssdp: ssdp_notify_updates_timestamp.