test_mock_pub_sub: increase wait time in mock pub/sub test for loaded systems

The msleep(1) in test_mock_pub_sub() can cause random failures onmachines under heavy load.
As this test seems to validates compatibility between different ZMTP version and not performance,
I propose Increase the wait time to allow the state machine to properly attach the pipe after handshake.

Note to simulate the overloaded machine in local I used:
stress-ng --cpu 24 --switch 16 --timer 8 --timeout 60s &
while tests/test_mock_pub_sub
do
    echo "PASS"
done

Author: Thomas-Barbier-1A

tests/test_mock_pub_sub.cpp

@@ -141,7 +141,7 @@ static void test_mock_pub_sub (bool sub_command_, bool mock_pub_)
         TEST_ASSERT_EQUAL_INT (0, rc);
         //  SUB binds, let its state machine run
         //  Because zeromq attach the pipe after the handshake, we need more time here before we can run the state-machine
-        msleep (1);
+        msleep (10);
         zmq_recv (server, buffer, 16, ZMQ_DONTWAIT);
 
         if (sub_command_) {