Rewrite and re-enable log_dump
This is major change which brings following changes:
- port log_dump to spawn() API
- fix: allow creating multiple log_dump reports at once
(by using separate/unique temporary directory)
NOTE: There is no guarantee that dump scripts are able to handle parallell
invocation!
- fix: always broadcast the signal about finished dump - even in case of
error (client should not wait indifinitely for status)
- move logic of moving crash-dump reports to separate script
Change-Id: I78585b9c3c6bfb9e12950985b389c0edf0eac7f0