logfile_helper: don't log strings, including the entire log file.
logfile_helper: don't log strings, including the entire log file.

Change-Id: Ia8f940e244b9a976deb8bb5a2c32348a85d77910

Linaro/lava-server,Linaro/lava-server,Linaro/lava-server,Linaro/lava-server