Fix code review issues

Author: alcaeus

src/libmongoc/tests/test-mongoc-error.c

@@ -185,7 +185,7 @@ test_state_change_helper (uint32_t domain, bool expect_error)
    }
 
    /* Fallback code that's used when no code was returned */
-   error.code = 17;
+   error.code = MONGOC_ERROR_QUERY_FAILURE;
    bson_strncpy (error.message, "... not master ...", sizeof (error.message));
    BSON_ASSERT (expect_error == _mongoc_error_is_not_master (&error));
    BSON_ASSERT (!_mongoc_error_is_recovering (&error));

src/libmongoc/tests/test-mongoc-topology.c

@@ -2053,7 +2053,7 @@ test_request_scan_on_error ()
               true /* should_scan */,
               true /* should_mark_unknown */,
               NULL /* server_err */);
-   /* for an unknown code, the message should still be checked. */
+   /* for an unknown code, the message should not be checked. */
    TEST_BOTH ("{'ok': 0, 'code': 12345, 'errmsg': 'not master'}",
               false /* should_scan */,
               false /* should_mark_unknown */,