The "BT" flag was not clear, so if the fly frame was first tbrl, then
switched to btlr, then this was changed back, the result was not tbrl
but tblr.

Change-Id: I9a258e64e7a6e5849edd5a6a21a6182f642e44ab
Reviewed-on: https://gerrit.libreoffice.org/72881
Tested-by: Jenkins
Reviewed-by: Miklos Vajna <vmiklos@collabora.com>