Fix bug #10229 - No access check verification on stream files.

Fix bug #10229 - No access check verification on stream files.

https://bugzilla.samba.org/show_bug.cgi?id=10229

We need to check if the requested access mask
could be used to open the underlying file (if
it existed), as we're passing in zero for the
access mask to the base filename.

Signed-off-by: Jeremy Allison <jra@samba.org>
Fix Bug #10235 - CVE-2013-4475: No access check verification on stream files.
https://bugzilla.samba.org/show_bug.cgi?id=10235
(cherry picked from commit 14d48130870579541c07f5a0f64638e635ddce95)