[Fix] Core: Fix address rotation bug

[Fix] Core: Fix address rotation bug

Previously, upstream.get_addr function returned the new address of the
upstream. Unfortunately, it was used for printing addresses. It caused
the following situation: let's imagine we have A1 and A2 where A1 was
initially selected. So the connection was performed to A1:

                           Current addr   Selected addr

   Connect+---------+      A2+------>A1   A1
                    |
+-+Print failure<---+      A1+------>A2   A2
|                        +----+
+->Mark failure+-------->+ A2 |
                         +----+

But the failure OP as well as log message told about `A2` where the real
problem happened with `A1`.

This commit adds distinguishing between getting the next and the current
address of the upstream resolving this issue.