fix to set file as default log destination if log_mode is not set in the config file (backwards compatibility)
fix to set file as default log destination if log_mode is not set in the config file (backwards compatibility)

toni-moreno/snmpcollector,toni-moreno/snmpcollector,toni-moreno/snmpcollector,toni-moreno/snmpcollector,toni-moreno/snmpcollector