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

test/functional/mining_basic.py

@@ -69,7 +69,7 @@ class MiningTest(BitcoinTestFramework):
         self.log.info('getmininginfo')
         mining_info = node.getmininginfo()
         assert_equal(mining_info['blocks'], 200)
-        assert_equal(mining_info['chain'], 'regtest')
+        assert_equal(mining_info['chain'], self.chain)
         assert 'currentblocktx' not in mining_info
         assert 'currentblockweight' not in mining_info
         assert_equal(mining_info['difficulty'], Decimal('4.656542373906925E-10'))