remove inputvarname in operator; test=develop

paddle/fluid/framework/operator.h

@@ -174,14 +174,6 @@ class ExecutionContext {
     return op_.Inputs(name).size();
   }
 
-  const std::string InputVarName(const std::string& name) const {
-    return op_.Input(name);
-  }
-
-  const std::string OutputVarName(const std::string& name) const {
-    return op_.Output(name);
-  }
-
   size_t OutputSize(const std::string& name) const {
     return op_.Outputs(name).size();
   }

paddle/fluid/operators/cudnn_lstm_op.cu.cc

@@ -292,7 +292,7 @@ class CudnnLSTMGPUKernel : public framework::OpKernel<T> {
       // multi-devices before the first running.
       // use parent scope to make cache persistable
       auto *scope = const_cast<framework::Scope *>(ctx.scope().parent());
-      auto cache_var_name = ctx.InputVarName("Cache");
+      auto cache_var_name = ctx.Inputs("Cache")[0];
       cache_var = scope->Var(cache_var_name);
     }
     CudnnRNNCache *cudnn_rnn_cache = nullptr;