astobj2: Create function to copy weak proxied objects from container.

Create ao2_container_dup_weakproxy_objs to perform a similar function to
ao2_container_dup.  This function expects the source container to have
weakproxy objects, inserts the associated non-weak objects into the
destination container.  Orphaned weakproxy objects are ignored.

Create test for this new function and for ao2_weakproxy_find.

Change-Id: I898387f058057e08696fe9070f8cd94ef3a27482