We should remove the comparison test framework entirely (see #10603).

Until we do that, let's make it a bit more debuggable. Currently, if there's an assert in the framework, it's very difficult to track down where we are in the test generator. Make the logging a bit better to help with debugging.

Before this PR:

```
→ ./p2p-fullblocktest.py
2017-10-09 14:05:11.302000 TestFramework (INFO): Initializing test directory /tmp/user/1000/testzdnax_yr
2017-10-09 14:05:11.557000 TestFramework.mininode (INFO): Connecting to Bitcoin Node: 127.0.0.1:11975
2017-10-09 14:05:11.712000 TestFramework.comptool (INFO): Test 1: PASS
2017-10-09 14:05:11.947000 TestFramework.comptool (INFO): Test 2: PASS
2017-10-09 14:05:12.057000 TestFramework.comptool (INFO): Test 3: PASS
2017-10-09 14:05:12.058000 TestFramework (ERROR): Assertion failed
Traceback (most recent call last):
  File "/home/ubuntu/bitcoin/test/functional/test_framework/test_framework.py", line 117, in main
    self.run_test()
  File "./p2p-fullblocktest.py", line 72, in run_test
    self.test.run()
  File "/home/ubuntu/bitcoin/test/functional/test_framework/comptool.py", line 306, in run
    assert test_number != 4
AssertionError
2017-10-09 14:05:12.059000 TestFramework (INFO): Stopping nodes
2017-10-09 14:05:14.203000 TestFramework (WARNING): Not cleaning up dir /tmp/user/1000/testzdnax_yr
2017-10-09 14:05:14.204000 TestFramework (ERROR): Test failed. Test logging available at /tmp/user/1000/testzdnax_yr/test_framework.log
```

With this PR:

```
→ ./p2p-fullblocktest.py
2017-10-09 14:03:54.069000 TestFramework (INFO): Initializing test directory /tmp/user/1000/testuey7t3tf
2017-10-09 14:03:54.329000 TestFramework.mininode (INFO): Connecting to Bitcoin Node: 127.0.0.1:11783
2017-10-09 14:03:54.383000 TestFramework.comptool (INFO): Running test 1: ./p2p-fullblocktest.py line 184
2017-10-09 14:03:54.496000 TestFramework.comptool (INFO): Running test 2: ./p2p-fullblocktest.py line 193
2017-10-09 14:03:54.758000 TestFramework.comptool (INFO): Running test 3: ./p2p-fullblocktest.py line 205
2017-10-09 14:03:54.867000 TestFramework.comptool (INFO): Running test 4: ./p2p-fullblocktest.py line 208
2017-10-09 14:03:54.867000 TestFramework (ERROR): Assertion failed
Traceback (most recent call last):
  File "/home/ubuntu/bitcoin/test/functional/test_framework/test_framework.py", line 117, in main
    self.run_test()
  File "./p2p-fullblocktest.py", line 72, in run_test
    self.test.run()
  File "/home/ubuntu/bitcoin/test/functional/test_framework/comptool.py", line 309, in run
    assert test_number != 4
AssertionError
2017-10-09 14:03:54.868000 TestFramework (INFO): Stopping nodes
2017-10-09 14:03:56.950000 TestFramework (WARNING): Not cleaning up dir /tmp/user/1000/testuey7t3tf
2017-10-09 14:03:56.950000 TestFramework (ERROR): Test failed. Test logging available at /tmp/user/1000/testuey7t3tf/test_framework.log
```