[REVIEW-3-6] fdo#55379, handle the lifetime of mpCondFormat correctly

[Markus Mohrhard]

Hey,

[1] fixes another problem with the cond format import for the old cond
format data structures. The style might be imported several times with
different ranges and therefore we may delete the mpCondFormat which is
then owned by the ptr_set in ScConditionalFormatList.

Regards,
Markus

[1] http://cgit.freedesktop.org/libreoffice/core/commit/?id=c5d4e2cf96e5c28634ed6968f87b476e8a2a5850