Merge #17893: qa: Fix double-negative arg test

8b2f471 qa: Fix double-negative arg test (Hennadii Stepanov)

Pull request description:

  Commit 67518f7cc61bf59ddfa0fd7c8dbbdec3653b9556 tests do not catch that a pointer is returned instead of a value.

  This PR makes test to not accept trailing characters after 0.

  From [IRC](http://www.erisian.com.au/bitcoin-core-dev/log-2020-01-07.html#l-358):
  >  \<hebasto\> ryanofsky: hmm, why test/functional/feature_config_args.py passed on 67518f7cc61bf59ddfa0fd7c8dbbdec3653b9556 ?
  >  \<hebasto\> I see now: test is broken.
  >  \<ryanofsky\> test should be unaffected by that change, do you see a break somewhere?
  >  \<hebasto\> yes: "-connect=0x7fff50369968" != "-connect=0"
  > ...
  >  \<ryanofsky\> Oh I see how that would happen, it should not be a problem in the current PR.
  >  \<hebasto\> going to submit a pr to fix test
  >  \<ryanofsky\> in the commit you mentioned, value is a pointer to a string, and it was printing the pointer address instead of the string on: LogPrintf("Warning: parsed potentially confusing double-negative -%s=%s\n", key, value);
  >  \<hebasto\> correct
  >  \<ryanofsky\> oh I see, test could be fixed to more robust and not accept trailing characters after 0

ACKs for top commit:
  ryanofsky:
    Code review ACK 8b2f471. I don't know how you found this but it's a nice catch! This change should make the test more reliable.

Tree-SHA512: 454b3d4415771d353a2da766f6ae6e0bfae7bdf485aaa7bfdd323595282356eeaf3f40e556b39f753bc35f578cbe9684368887eef2d63c5d7f0d7d9fa971697a

Author: fanquake

test/functional/feature_config_args.py

@@ -79,7 +79,7 @@ def test_config_file_parser(self):
             conf.write('')  # clear
 
     def test_log_buffer(self):
-        with self.nodes[0].assert_debug_log(expected_msgs=['Warning: parsed potentially confusing double-negative -connect=0']):
+        with self.nodes[0].assert_debug_log(expected_msgs=['Warning: parsed potentially confusing double-negative -connect=0\n']):
             self.start_node(0, extra_args=['-noconnect=0'])
         self.stop_node(0)