Change the prototype of the vfs function get_nt_acl().

Change the prototype of the vfs function get_nt_acl().

Up to now, get_nt_acl() took a files_struct pointer (fsp) and
a file name. All the underlying functions should need and now
do need (after the previous preparatory work), is a connection_struct
and a file name. The connection_struct is already there in the
vfs_handle passed to the vfs functions. So the files_struct
argument can be eliminated.

This eliminates the need of calling open_file_stat in a couple
of places to produce the fsp needed.

Michael