handle .doc cropping also inside groups (fdo#38411)

Writer does handle cropping on its own, but only for "toplevel" images,
not for those inside groups, so there still use the generic code.

Change-Id: I805a4cbd2d4cea7008e0322688ccd7f35a6d4a2c
(cherry picked from commit af51f3fb5aee469423b154958ccb3fe61284122f)
Reviewed-on: https://gerrit.libreoffice.org/8950
Reviewed-by: Miklos Vajna <vmiklos@collabora.co.uk>
Tested-by: Miklos Vajna <vmiklos@collabora.co.uk>