Clear hold shelf process should also process already-canceled holds (that are still on the shelf)

[Bill Erickson]

On the heels of #872533, which added support for displaying canceled holds that are still physically on the holds shelf within the hold shelf browse interface, I'd like to add support for processing canceled holds in the clear-shelf process.

My goals:

1. Copies attached to the already-canceled holds will pick up the custom clear-shelf copy status if one is configured.
2. The already-canceled holds will show up in the shelf browser after the clear-shelf process is run, grouped along with other newly-canceled holds.
3. Already-canceled holds will not be re-canceled during the clear-shelf process. That part of the process will be skipped.

Topic branch to follow...

[Bill Erickson (berick)]

Topic branch pushed to user/berick/clear-hold-shelf-process-canceled @ working.

[Thomas Berezansky (tsbere)]

Worked in my testing, pushed.