Fix getitems slice bug (#18053)

* fix get items slice bug; test=develop

* fix unique_name bug; test=develop

python/paddle/fluid/framework.py

@@ -756,10 +756,8 @@ class Variable(object):
     def _cloneVar(self, copy=False):
         if not copy:
             return self.block.create_var(
-                name=unique_name.generate(".".join(self.name)),
-                dtype=self.dtype,
-                persistable=self.persistable,
-                stop_gradient=self.stop_gradient, )
+                name=unique_name.generate_with_ignorable_key(self.name),
+                dtype=self.dtype)
         else:
             return self