btrfs: Cleanup the btrfs_parse_options for remount.

Since remount will pending the new mount options to the original mount
options, which will make btrfs_parse_options check the old options then
new options, causing some stupid output like "enabling XXX" following by
"disable XXX".

This patch will add extra check before every btrfs_info to skip the
output from old options checking.

Signed-off-by: Qu Wenruo <quwenruo@cn.fujitsu.com>
Signed-off-by: Josef Bacik <jbacik@fb.com>
Signed-off-by: Chris Mason <clm@fb.com>