Btrfs: only inherit btrfs specific flags when creating files

Btrfs: only inherit btrfs specific flags when creating files

Xfstests 79 was failing because we were inheriting the S_APPEND flag when we
weren't supposed to.  There isn't any specific documentation on this so I'm
taking the test as the standard of how things work, and having S_APPEND set on a
directory doesn't mean that S_APPEND gets inherited by its children according to
this test.  So only inherit btrfs specific things.  This will let us set
compress/nocompress on specific directories and everything in the directories
will inherit this flag, same with nodatacow.  With this patch test 79 passes.
Thanks,

Signed-off-by: Josef Bacik <josef@redhat.com>
(cherry picked from commit e27425d614d68daa08f60735982a7c3a0230e855)