fstests: fix various $seqres.full issues

fstests: fix various $seqres.full issues

There're many tests don't remove $seqres.full before writing to it, and
accumulating logs there, then the logs are always growing over time.
Let's fix them once.

generic/16[1-8] generic/170 and generic/33[34] truncate $seqres.full in
the middle of the test, which results in partial logs. Fix them as well.

xfs/227 has duplicated lines to remove $seqres.full, remove the extra
line.

Signed-off-by: Eryu Guan <eguan@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>