upnp: code improvements and bug fixes

This patch adds many improvements and bug fixes:
1- For PUPNP lib, use the synchronous methods for add and remove
requests. The async versions have many issues mainly at shutdown.
If the callbacks do not arrive on time, the memory allocated by
the lib when performing the request will leak.
2- Rework the init and IGD search of PUPNP.
3- Move the termination step (for libupnp in particular) from
the destructor to a newly added method (termiinate()). This will
prevent a race at shutdown between libupnp threads (callbacks) and
the daemon shutdown process.
4- Do not try to initialize libupnp if the host address is invalid.
This will prevent putting the lib in an unstable state.

Gitlab: #472

Change-Id: I14e5ddcd2b735da374a1f09bcef40f6a86a38133