s3-spoolss: fix printer_driver_files_in_use() call ordering

s3-spoolss: fix printer_driver_files_in_use() call ordering

printer_driver_files_in_use() performs two tasks: it returns whether any
of the files in the to-be-deleted driver overlap with other drivers, it
also trims such files from the info structure passed in.

In processing a DeletePrinterDataEx request with DPD_DELETE_UNUSED_FILES
set, printer_driver_files_in_use() must be called to ensure files in
use by other drivers are not removed.

https://bugzilla.samba.org/show_bug.cgi?id=4942
(cherry picked from commit 8e3c0ac2815bc25360bf408c50449d154b841f8a)