[oneDNN][BUG FIX] Fix to mkl_eager_op_rewrite_test
This PR fixes a failure to the test `//tensorflow/core/common_runtime/eager:mkl_eager_op_rewrite_test`. The test runs with `--config=mkl`. It is failing due to a recent change to `EagerContext`(https://github.com/tensorflow/tensorflow/commit/ee855630f68e6fbfee334fb9ce3aab7f4dbad16a).

In order to fix, this PR updates the test with `tsl::core::RefCountPtr<tensorflow::IntraProcessRendezvous>` instead of raw pointer.