net: also wait for exceptional events in Sock::Wait()

This mimics closely `CConnman::SocketEvents()` and the underlying
`poll(2)`.

src/i2p.cpp

@@ -150,8 +150,8 @@ bool Session::Accept(Connection& conn)
                 throw std::runtime_error("wait on socket failed");
             }
 
-            if ((occurred & Sock::RECV) == 0) {
-                // Timeout, no incoming connections within MAX_WAIT_FOR_IO.
+            if (occurred == 0) {
+                // Timeout, no incoming connections or errors within MAX_WAIT_FOR_IO.
                 continue;
             }