ktask: add undo support

hulk inclusion
category: feature
bugzilla: 13228
CVE: NA
---------------------------

Tasks can fail midway through their work.  To recover, the finished
chunks of work need to be undone in a task-specific way.

Allow ktask clients to pass an "undo" callback that is responsible for
undoing one chunk of work.  To avoid multiple levels of error handling,
do not allow the callback to fail.  For simplicity and because it's a
slow path, undoing is not multithreaded.

Signed-off-by: Daniel Jordan <daniel.m.jordan@oracle.com>
Signed-off-by: Hongbo Yao <yaohongbo@huawei.com>
Reviewed-by: Xie XiuQi <xiexiuqi@huawei.com>
Tested-by: Hongbo Yao <yaohongbo@huawei.com>
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>