MXS-2414: Add test case

Added a test that checks the host blocking is triggered and it blocks even
successful authentication attemps.

maxscale-system-test/mxs2414_host_blocking.cpp

@@ -0,0 +1,47 @@
+/**
+ * MXS-2414: Block host after repeated authentication failures
+ * https://jira.mariadb.org/browse/MXS-2414
+ */
+
+#include "testconnections.h"
+
+int main(int argc, char* argv[])
+{
+    TestConnections test(argc, argv);
+    bool found = false;
+
+    for (int i = 0; i < 1000; i++)
+    {
+        test.set_timeout(30);
+        auto c = test.maxscales->rwsplit();
+        c.set_credentials("wrong-user", "wrong-pw");
+        test.expect(!c.connect(), "Connection should fail");
+
+        if (strstr(c.error(), "temporarily blocked due to too many authentication failures"))
+        {
+            test.tprintf("Got correct error: %s", c.error());
+            found = true;
+
+            // Make sure some valid logins are blocked.  Note that this part is not fully deterministic which
+            // means we cannot interpret a lack of authentication failures as a sign of a problem. The only
+            // thing we can check is that, in case an authentication failure occurs, the correct error is
+            // returned.
+            for (int j = 0; j < 100; j++)
+            {
+                auto c2 = test.maxscales->rwsplit();
+
+                if (!c2.connect())
+                {
+                    test.expect(strstr(c2.error(), "temporarily blocked due to too many authentication failures"),
+                                "The same error should be returned: %s", c2.error());
+                    break;
+                }
+            }
+            break;
+        }
+    }
+
+    test.expect(found, "Host should be blocked");
+
+    return test.global_result;
+}