printing: Handle jobs canceled at printer

When a job is canceled on the printer front panel, some printers will
report it as completed.  Since not all the pages have been printed in
this case, this triggers a DCHECK.  Instead of doing a DCHECK, treat
the case of a completed job with an incomplete set of pages as canceled.

Bug: 417763388
Test: Print and cancel at various stages
Change-Id: I5c0647d66876c6b409ab41ff7f5af523bdf4e45b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6553241
Reviewed-by: Paul Moy <pmoy@chromium.org>
Commit-Queue: Benjamin Gordon <bmgordon@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1463436}