message: host_embedding_lookup_test: Use a non-resource variable in TF2
  Summary:
  Fixes the following error in r2.1:
  TypeError: 'IpuHostEmbedding' Op requires that input 'ref' be a
  mutable tensor but was ['tf.float32'] (e.g.: a tf.Variable)
  Reviewers: #tensorflow, jakeh
diff: @@ -55,7 +55,10 @@ class HostEmbeddingLookupTest(test_util.TensorFlowTestCase):
  with ops.device('cpu'):
  i = array_ops.placeholder(np.int32, [lookup_count])
  - w = variable_scope.get_variable("foo", dtype=np.float32, shape=shape)
  + w = variable_scope.get_variable("foo",
  + dtype=np.float32,
  + shape=shape,
  + use_resource=False)
  with ipu.scopes.ipu_scope("/device:IPU:0"):
  r = ipu.ipu_compiler.compile(my_net, inputs=[i])
  @@ -104,7 +107,10 @@ class HostEmbeddingLookupTest(test_util.TensorFlowTestCase):
  with ops.device('cpu'):
  i = array_ops.placeholder(np.int32, [lookup_count])
  - w = variable_scope.get_variable("foo", dtype=np.float32, shape=shape)
  + w = variable_scope.get_variable("foo",
  + dtype=np.float32,
  + shape=shape,
  + use_resource=False)
  with ipu.scopes.ipu_scope("/device:IPU:0"):
  r = ipu.ipu_compiler.compile(my_net, inputs=[i])
  