utils/wa_results_collector: Fix typo for log
Created by: Leo-Yan
When run wa_results_collector class, it report the error for log: AttributeError: 'WaResultsCollector' object has no attribute 'log'
This is caused by the typo "self.log.warning", so fix typo to "self._log.warning".
Signed-off-by: Leo Yan leo.yan@linaro.org