tree: use cache.tree to check if cache file exists (#4244)

Continuing #4050 This issue was found in #4242

Author: efiop

dvc/tree/base.py

@@ -271,7 +271,9 @@ def get_hash(self, path_info, tree=None, **kwargs):
         if (
             hash_
             and self.is_dir_hash(hash_)
-            and not tree.exists(self.cache.tree.hash_to_path_info(hash_))
+            and not self.cache.tree.exists(
+                self.cache.tree.hash_to_path_info(hash_)
+            )
         ):
             hash_ = None