libmultipath: do not access dm structures after dm_task_destroy
libmultipath: do not access dm structures after dm_task_destroy

device-mapper has the habit of freeing up all internal structures
after dm_task_destroy. So we shouldn't try to access any of these
later on.

References: bnc#672857

Signed-off-by: Hannes Reinecke <b0d1e9e4a4e27620745ff49be9000da3174a4cc6@suse.de>

unakatsuo/multipath-tools,vijaychauhan/multipath-tools,vijaychauhan/multipath-tools,unakatsuo/multipath-tools,unakatsuo/multipath-tools