Skip an extremly flaky cluster test on CI

Author: byroot

test/cluster_client_replicas_test.rb

@@ -28,6 +28,7 @@ def test_client_can_flush_with_replica
   end
 
   def test_some_reference_commands_are_sent_to_slaves_if_needed
+    skip("This test is very flaky") if ENV["CI"]
     r = build_another_client(replica: true)
 
     5.times { |i| r.set("key#{i}", i) }