check-sof-logger need to report fail is no valid log shows

[xiulipan]

From latest test result. logger on legacy platform is not working but the test result of check-sof-logger still show pass. Need to fix the issue in check-sof-logger

2020-07-29 02:09:31 UTC [REMOTE_INFO] Found file: /usr/bin/sof-logger 96b4a1605636506fab8cfbac4396f7ce
2020-07-29 02:09:31 UTC [REMOTE_INFO] Checking ldc File: /etc/sof/sof-bdw.ldc ...
2020-07-29 02:09:31 UTC [REMOTE_INFO] Found file: /etc/sof/sof-bdw.ldc 6d96f9315129a366644043bbaab6a96b
2020-07-29 02:09:31 UTC [REMOTE_INFO] Try to dump the dma trace log via sof-logger ...
2020-07-29 02:09:31 UTC [REMOTE_COMMAND] sudo /usr/bin/sof-logger -t -l /etc/sof/sof-bdw.ldc -o /home/ubuntu/sof-test/logs/check-sof-logger/2020-07-29-10:09:31-5838/logger.data.log 2> /home/ubuntu/sof-test/logs/check-sof-logger/2020-07-29-10:09:31-5838/logger.error.log &
2020-07-29 02:09:33 UTC [REMOTE_COMMAND] sudo pkill -9 sof-logger
2020-07-29 02:09:34 UTC [REMOTE_INFO] Log data BEG>>
         TIMESTAMP              DELTA C# COMPONENT          LOCATION                      CONTENT
2020-07-29 02:09:34 UTC [REMOTE_INFO] <

[mengdonglin]

Same requirement as #297