Revert "s4:samdb python bindings - we don't need the attributes here"

This reverts commit 53ef426e6f.

As abartlet pointed out this causes to load all attributes and therefore gives
us more here than we need (only the check for the DN)!

source4/scripting/python/samba/samdb.py

@@ -165,7 +165,8 @@ pwdLastSet: 0
             assert(domain_dn is not None)
 
             res = self.search(domain_dn, scope=ldb.SCOPE_SUBTREE, 
-                              expression=filter)
+                              expression=filter,
+                              attrs=[])
             assert(len(res) == 1)
             user_dn = res[0].dn