report-fossil: Be more robust when guessing the driver

When running ./fossil_replay.sh with --graphics-pipeline-range 0 0
--compute-pipeline-range 0 0, the script will append lines which don't
contain any driver specific columns. Read rows until we are able to guess
the driver instead of aborting after the first row.

Reviewed-by: Rhys Perry <pendingchaos02@gmail.com>