btrfs/192: use append operator to output log replay results to $seqres.full

btrfs/192: use append operator to output log replay results to $seqres.full

After doing log replay, btrfs/192 is overwriting the $seqres.full file
because it uses the plain ">" redirect operator, instead of an append
">>" redirect operator. As a consequence it is overriding the file and
eliminating any previous output that may be useful to debug a test
failure (such as the fsstress seed or mkfs results). So use >> instead
of >.

Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: Anand Jain <anand.jain@oracle.com>
Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: Zorro Lang <zlang@kernel.org>