We collect all file locks to a golbal list, so we can use them easily
in dump_one_task. For optimizaton, we only collect file locks hold by
tasks in the pstree.

Thanks to the ptrace-seize machanism, we can aviod the blocked file lock
issue, makes the work simpler.

Right now, the check handles only one situation:
-- Dumping tasks with file locks hold without the -l option.

This covers for the most part. But we still need some more work to make
it perfect robust in the future.
Signed-off-by: Qiang Huang <h.huangqiang@huawei.com>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>