vfs: kernel_flock and named streams

vfs: kernel_flock and named streams

Streams implementing VFS modules may implement streams in a way that the
fsp will have the basefile open in the fsp fd, so lacking a distinct fd
for the stream, kernel_flock will apply on the basefile which is
wrong. The actual check is deffered to the VFS module implementing the
kernel_flock call.

Bug: https://bugzilla.samba.org/show_bug.cgi?id=11243

Signed-off-by: Ralph Boehme <slow@samba.org>
Reviewed-by: Jeremy Allison <jra@samba.org>