CreateKeyValue with RePublish will fail if KV already exists

This cannot be updated in the server at the moment, so if user
calls CreateKeyValue() with a config that does not have RePublish
and then call again on the same bucket with RePublish set, the
user will get an error. Added a test that shows that this is the case.

Signed-off-by: Ivan Kozlovic <ivan@synadia.com>

kv_test.go

@@ -120,6 +120,22 @@ func TestKeyValueRePublish(t *testing.T) {
 	defer nc.Close()
 
 	kv, err := js.CreateKeyValue(&KeyValueConfig{
+		Bucket: "TEST_UPDATE",
+	})
+	if err != nil {
+		t.Fatalf("Error creating store: %v", err)
+	}
+	// This is expected to fail since server does not support as of now
+	// the update of RePublish.
+	kv, err = js.CreateKeyValue(&KeyValueConfig{
+		Bucket:    "TEST_UPDATE",
+		RePublish: &RePublish{Source: ">", Destination: "bar.>"},
+	})
+	if err == nil {
+		t.Fatal("Expected failure, did not get one")
+	}
+
+	kv, err = js.CreateKeyValue(&KeyValueConfig{
 		Bucket:    "TEST",
 		RePublish: &RePublish{Source: ">", Destination: "bar.>"},
 	})