upnp: improve IGD search

This patch introduces the following  modifcations:
1- The search for IGD and all requests will be  performed only
if the local address is valid.
2- A new search retry mechanism was introduced (similar to nat-pmp)
to improve resilience against transient failures, in particular
during a connectivity change. The search is perfomed a pre-defined
number of times before it is definitely set as failed.
3- The device UID was used to identify the IGD. However, some
devices may have more than one IGD with the same device ID, which
caused some of IGDs to wrongly ignored. This is problematic if the
first IGD with the same device ID that was added does not pass
the validation or does not respond successfully to mapping
requests. Now, we use both the deviceId and the URL as identifier
for the discoverd IGDs.
4- Mapping address management was simplified.
5- ICE will only considere mappings that have valid local address.

Gitlab: #420

Change-Id: I7eed337e9c1a190f6c42ebb1381957660f604410