Modified demo smb.conf to not have /tmp writeable by everyone by default.

According to server-linux some people seem to be uncommenting the example
[tmp] without thinking what it does  :-)

Dan
(This used to be commit c290c229f9)

examples/simple/smb.conf

@@ -80,11 +80,13 @@
    writable = no
    create mode = 0700
 
-; you might also want this one
+; you might also want this one, notice that it is read only so as not to give
+; people without an account write access. 
+;
 ; [tmp]
 ;   comment = Temporary file space
 ;   path = /tmp
-;   read only = no
+;   read only = yes
 ;   public = yes
 
 ;