Fix CI unit tests (#5196)

- Add retries for rpc client
- Add dynamic port allocation for rpc servers

src/test/jtx/impl/WSClient.cpp

@@ -69,6 +69,10 @@ class WSClientImpl : public WSClient
             if (pp.ip && pp.ip->is_unspecified())
                 *pp.ip = pp.ip->is_v6() ? address{address_v6::loopback()}
                                         : address{address_v4::loopback()};
+
+            if (!pp.port)
+                Throw<std::runtime_error>("Use fixConfigPorts with auto ports");
+
             return {*pp.ip, *pp.port};
         }
         Throw<std::runtime_error>("Missing WebSocket port");