drbd: remove call to memset before free device/resource/connection

This revert c2258ffc ("drbd: poison free'd device, resource and
connection structs"), add memset is odd here for debugging, there are
some methods to accurately show what happened, such as kdump.

Signed-off-by: Wang ShaoBo <bobo.shaobowang@huawei.com>
Link: https://lore.kernel.org/r/20221124015817.2729789-2-bobo.shaobowang@huawei.com


Signed-off-by: Jens Axboe <axboe@kernel.dk>