s3-printing: Fix driver upload for Xerox 4110 PS printer driver.

s3-printing: Fix driver upload for Xerox 4110 PS printer driver.

We need to allow to set filesystem capabilities from the default vfs in
create_conn_struct() in order to find mixed-case filenames. Thanks Volker!

This one was hard to find, so a little longer explanation:

When a Windows client tries to upload e.g. the Xerox 4110 PS driver, the client
first uploads the driver files to the [print$] share. Some of them (in this case
the Windows Postscript drivers) are with uppercase filenames while some of them
(like the PPD file) are in lowercase. After the driver upload the client issues
the spoolss_AddPrinterDriverEx() call with level 6. There the client tries to
add the PPD file with an uppercase filename (while having stored it in lowercase
on the server). The internal spoolss add driver functions then could not find the
appropriate filename while trying to move them to the version subdirectory (in
this case W32X86/3) and fails then entire spoolss_AddPrinterDriverEx() call.
With this fix, the convert_unix_name() name finds the correct file and
the spoolss_AddPrinterDriverEx() succeeds.

Guenther
(cherry picked from commit fe839b65a7b4e8d5e085287b7d33ee1f970fe7c2)