[t:4039], set a default cachetable size

git-svn-id: file:///svn/toku/tokudb@35574 c7de825b-a66e-492c-adef-691d508d4ae1

src/tests/threaded_stress_test_helpers.h

@@ -694,6 +694,7 @@ static const struct cli_args DEFAULT_ARGS = {
     .time_of_test = 180,
     .node_size = 4096,
     .basement_node_size = 1024,
+    .cachetable_size = 300000;
     .only_create = false,
     .only_stress = false,
     .checkpointing_period = 10,