Merge #14805: tests: Support calling add_nodes more than once

98a1846b00 tests: Support calling add_nodes more than once (Steven Roose)

Pull request description:

  Ran into this while writing [a multi-chain test for Elements](https://github.com/ElementsProject/elements/pull/458) where I call this method more than once.

Tree-SHA512: f2d698fcb560552aa5d81a4c3fbf40b7269b228b34d85a118291649ef83f8c0a30cd82a28d418237b55893bcecd538046b704e64a4d8a41f2c0aef8033dc83e5

test/functional/test_framework/test_framework.py

@@ -294,7 +294,8 @@ class BitcoinTestFramework(metaclass=BitcoinTestMetaClass):
         assert_equal(len(extra_args), num_nodes)
         assert_equal(len(binary), num_nodes)
         for i in range(num_nodes):
-            self.nodes.append(TestNode(i, get_datadir_path(self.options.tmpdir, i), rpchost=rpchost, timewait=self.rpc_timewait, bitcoind=binary[i], bitcoin_cli=self.options.bitcoincli, mocktime=self.mocktime, coverage_dir=self.options.coveragedir, extra_conf=extra_confs[i], extra_args=extra_args[i], use_cli=self.options.usecli))
+            numnode = len(self.nodes)
+            self.nodes.append(TestNode(numnode, get_datadir_path(self.options.tmpdir, numnode), rpchost=rpchost, timewait=self.rpc_timewait, bitcoind=binary[i], bitcoin_cli=self.options.bitcoincli, mocktime=self.mocktime, coverage_dir=self.options.coveragedir, extra_conf=extra_confs[i], extra_args=extra_args[i], use_cli=self.options.usecli))
 
     def start_node(self, i, *args, **kwargs):
         """Start a bitcoind"""