Add 'DeleteFailedTaskAfter' config variable and section to retrace-server-cleanup

Failed tasks often take up a significant amount of space due to the fact that
the task often gets submitted multiple times in hopes one time it will succeed.

We don't want to keep failed tasks around for nearly as long as successful tasks
which are just old, so it makes sense to have a separate config variable and
section in the cleanup script.

Tested on a development retrace-server system which had older failed tasks
by gradually lowering the value of DeleteFailedTaskAfter and repeatedly running
retrace-server-cleanup manually.

Should fix https://bugzilla.redhat.com/show_bug.cgi?id=1086321

Signed-off-by: Dave Wysochanski <dwysocha@redhat.com>
Signed-off-by: Michal Toman <mtoman@redhat.com>
add DeleteFailedTaskAfter to config file

Signed-off-by: Michal Toman <mtoman@redhat.com>
Move stat and chmod after all vmcore extraction and stripping is done.

The previous attempt at fixing the following bug was incorrect:
https://bugzilla.redhat.com/show_bug.cgi?id=1076833

Move the stat and chmod to the very end, after all vmcore extraction
and stripping (makedumpfile) processing is done.  The previous patch
did not catch the case where makedumpfile was run, and also messed
up the log message which calculated the space saved by makedumpfile
(it always said "Makedumpfile ... saved 0 bytes" after the last change).

Moving the stat and the chmod to the very end of all processing is
where it should be.
Fixes https://bugzilla.redhat.com/show_bug.cgi?id=1076833

Signed-off-by: Dave Wysochanski <dwysocha@redhat.com>
Signed-off-by: Michal Toman <mtoman@redhat.com>