The case when a fly frame was first constructed with one direction then
switched to btlr was already working.

The case when the direction is already set before the SwFlyFrame is
constructed was not, as SvxFrameDirection::Vertical_LR_BT was unhandled.

Change-Id: I97d15b3fc15ee116181718144dc9bccf8f31529f
Reviewed-on: https://gerrit.libreoffice.org/72077
Tested-by: Jenkins
Reviewed-by: Miklos Vajna <vmiklos@collabora.com>