Rollback of: tensorflow: switch to eigen thread pool

This is first step of switching tensorflow to the new
non-blocking thread pool in eigen.

TESTED:
  - passed opensource_build
Change: 120376183

tensorflow/core/BUILD

@@ -642,7 +642,6 @@ cc_library(
         }),
     hdrs = ANDROID_TF_LITE_HDRS,
     copts = tf_copts() + ["-Os"],
-    defines = ["TENSORFLOW_USE_EIGEN_THREADPOOL"],
     tags = [
         "manual",
         "notap",
@@ -771,7 +770,6 @@ cc_library(
         "platform/tracing.h",
     ],
     copts = tf_copts(),
-    defines = ["TENSORFLOW_USE_EIGEN_THREADPOOL"],
     linkopts = ["-ldl"],
     deps = [
         ":protos_all_cc",

tensorflow/core/lib/core/threadpool.cc

@@ -17,6 +17,7 @@ limitations under the License.
 
 #ifdef TENSORFLOW_USE_EIGEN_THREADPOOL
 #define EIGEN_USE_THREADS
+#define EIGEN_USE_CUSTOM_THREAD_POOL
 #include "third_party/eigen3/unsupported/Eigen/CXX11/Tensor"
 #else
 #include <deque>