Fix docstrings in qa tests

This commit fixes the module-level docstrings for the tests and helper
modules in qa. Many of these tests were uncommented previously - this
commit ensures that every test case has at least a minimum level of
commenting.

qa/rpc-tests/disablewallet.py

@@ -2,10 +2,11 @@
 # Copyright (c) 2015-2016 The Bitcoin Core developers
 # Distributed under the MIT software license, see the accompanying
 # file COPYING or http://www.opensource.org/licenses/mit-license.php.
+"""Test a node with the -disablewallet option.
 
-#
-# Exercise API with -disablewallet.
-#
+- Test that validateaddress RPC works when running with -disablewallet
+- Test that it is not possible to mine to an invalid address.
+"""
 
 from test_framework.test_framework import BitcoinTestFramework
 from test_framework.util import *
@@ -24,7 +25,6 @@ class DisableWalletTest (BitcoinTestFramework):
         self.sync_all()
 
     def run_test (self):
-        # Check regression: https://github.com/bitcoin/bitcoin/issues/6963#issuecomment-154548880
         x = self.nodes[0].validateaddress('3J98t1WpEZ73CNmQviecrnyiWrnqRhWNLy')
         assert(x['isvalid'] == False)
         x = self.nodes[0].validateaddress('mneYUmWYsuk7kySiURxCi3AGxrAqZxLgPZ')