Problem: various tests fail in slow environments

Solution: add msleep (SETTLE_TIME) to test_immediate, test_spec_rep
and test_spec_router after the sockets are created and connected to
avoid failing when running in slower environment like through
Valgrind in underpowered VMs.

tests/test_immediate.cpp

@@ -67,6 +67,8 @@ int main (void)
     rc = zmq_connect (from, "tcp://localhost:6555");
     assert (rc == 0);
 
+    msleep (SETTLE_TIME);
+
     // We send 10 messages, 5 should just get stuck in the queue
     // for the not-yet-connected pipe
     for (int i = 0; i < 10; ++i) {