Skip not return_merged cases for standalone executor (#44810)

python/paddle/fluid/executor.py

@@ -1431,7 +1431,7 @@ class Executor(object):
 
         # NOTE: This is an experimental feature. If `export FLAGS_USE_STANDALONE_EXECUTOR=1 `,
         # use StandaloneExecutor to run the program.
-        if self._enable_interpreter_core and _can_use_interpreter_core(
+        if return_merged and self._enable_interpreter_core and _can_use_interpreter_core(
                 program, self.place):
             inner_program = program._program if isinstance(
                 program, compiler.CompiledProgram) else program