Replaced etcd2 with zk for end to end tests

Signed-off-by: Saif Alharthi <saif@saifalharthi.me>

go/mysql/query_test.go

@@ -154,6 +154,7 @@ func TestComStmtPrepare(t *testing.T) {
 	sConn.PrepareData = make(map[uint32]*PrepareData)
 	sConn.PrepareData[prepare.StatementID] = prepare
 
+	// write the response to the client
 	if err := sConn.writePrepare(result, prepare); err != nil {
 		t.Fatalf("sConn.writePrepare failed: %v", err)
 	}

test/utils.py

@@ -115,7 +115,7 @@ def add_options(parser):
       help='Leave the global processes running after the test is done.')
   parser.add_option('--mysql-flavor')
   parser.add_option('--protocols-flavor', default='grpc')
-  parser.add_option('--topo-server-flavor', default='etcd2')
+  parser.add_option('--topo-server-flavor', default='zk')
   parser.add_option('--vtgate-gateway-flavor', default='discoverygateway')