[2/3] shlwapi/tests: pass the STGM mode as a single flag to the tests, don't split it up.

[Reece Dunn]

This patch makes it easier to see the exact STGM mode being passed to
the SHCreateStreamOnFile methods, allowing it to be more generic. It
is part of cleanup to support testing the STGM sharing mode flags in
the final patch.

- Reece