If cache is initialized successfully, `struct _cache_mngt_attach_context` might
be freed in `cache_mngt_init_instance()`. In such case pointer to rollback
thread can't be accessed and thread can't be stopped.
To prevent such scenario pointer should be kept in separate variable.
Signed-off-by: Michal Mielewczyk <michal.mielewczyk@intel.com>
975ec6f32a