btrfs: add fstests to write 128k to a RST filesystem

btrfs: add fstests to write 128k to a RST filesystem

Add a test writing 128k to a file on an empty filesystem formatted with a
raid-stripe-tree.

Reviewed-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: Anand Jain <anand.jain@oracle.com>
Signed-off-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Anand Jain <anand.jain@oracle.com>
[Fixed the test statement and trailing white space in the .out file.]
Signed-off-by: Zorro Lang <zlang@kernel.org>