Added a function that flushes all logfiles synchronously.
Removed unnecessary debug information and return values.
Renamed and improved the synchronous log flushing function.
Changed to a skygw_message_t in skygw_log_sync_all.
Fixed some logs not being flushed
Merge remote-tracking branch 'origin/develop' into sync_log_flush
Merge pull request #68 from mariadb-corporation/sync_log_flush

Synchronized flushing of all logs