jqueue._LoadJobFromDisk: remove safety archival

Currently _LoadJobFromDisk archives job files it finds corrupted. Since
we want to use it to load files without holding locks, this could cause
a conflict: we just move the feature to _LoadJobUnlocked which is always
called with the lock held.

Signed-off-by: Guido Trotter <ultrotter@google.com>
Reviewed-by: Iustin Pop <iustin@google.com>