Fixing http tests to avoid hanging when assertions fail

[mbargiel]

The Mocha tests for the http adapter are asynchronous and rely on Mocha's done callback to be invoked on success - or failure. When it's not called, the tests hang. I identified various places where done was not being called, or was called incorrectly (ie never actually being reachable).

Here are two examples of handling that wasn't correct:

      axios.get('http://localhost:4444/').then(function (res) {
        assert.deepEqual(res.data, data);
        done(); // <-- this is never called if the `axios.get` promise is rejected. 
                // It's also not called if `assert.deepEqual` fails, because it 
                // throws. When `done` is used, Mocha treats the test function 
                // as asynchronous and does not handle exceptions
                // as the end of the test.
      })

        .catch(function (error) { 
          assert.ifError(error); // <-- !? rejected promises should have something passed to them, normally
          done(); // <-- this is never called, unless the promise was rejected with `undefined` or `null`
        });

This PR does not fix all occurrences, but all those from cases similar to the above. A future pass should be done on tests that are event-based to make sure done(error) is called in the proper places.

Ref: mentioned in issue #4318.

[mbargiel]

Review pointers

[jasonsaayman]

Thanks for this contribution