Tests: Use self.chain instead of 'regtest' in almost all current tests

test/functional/wallet_reorgsrestore.py

@@ -90,7 +90,7 @@ class ReorgsRestoreTest(BitcoinTestFramework):
         # Node0 wallet file is loaded on longest sync'ed node1
         self.stop_node(1)
         self.nodes[0].backupwallet(os.path.join(self.nodes[0].datadir, 'wallet.bak'))
-        shutil.copyfile(os.path.join(self.nodes[0].datadir, 'wallet.bak'), os.path.join(self.nodes[1].datadir, 'regtest', 'wallet.dat'))
+        shutil.copyfile(os.path.join(self.nodes[0].datadir, 'wallet.bak'), os.path.join(self.nodes[1].datadir, self.chain, 'wallet.dat'))
         self.start_node(1)
         tx_after_reorg = self.nodes[1].gettransaction(txid)
         # Check that normal confirmed tx is confirmed again but with different blockhash