scripted-diff: Use blocks_path where possible

-BEGIN VERIFY SCRIPT-
  sed -i 's|].chain_path, .blocks.|].blocks_path|g' $(git grep -l chain_path)
-END VERIFY SCRIPT-

test/functional/wallet_backup.py

@@ -226,7 +226,7 @@ class WalletBackupTest(BitcoinTestFramework):
             self.erase_three()
 
             #start node2 with no chain
-            shutil.rmtree(os.path.join(self.nodes[2].chain_path, 'blocks'))
+            shutil.rmtree(os.path.join(self.nodes[2].blocks_path))
             shutil.rmtree(os.path.join(self.nodes[2].chain_path, 'chainstate'))
 
             self.start_three(["-nowallet"])