Rewrite and re-enable log_dump

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