pool: Do not save terminated jobs to setup file

Without this patch, cancelled permanent jobs will resurrect after a
pool restart. Also fixes the 'migration clear' command to remove
failed jobs too.

Target: trunk
Request: 2.7
Request: 2.6
Require-book: no
Require-notes: yes
Acked-by: Paul Millar <paul.millar@desy.de>
Patch: http://rb.dcache.org/r/6420/
(cherry picked from commit 9ba476abe7b1432c4300b12edc36a57c2f150e18)
Merge pull request #380 from gbehrmann/fix/2.7/rb6420

pool: Do not save terminated jobs to setup file