PY3: dict doesn't have has_key

Signed-off-by: Noel Power <noel.power@suse.com>
Reviewed-by: Andrew Bartlett <abartlet@samba.org>
(cherry picked from Samba commit 82c84513331da9d0f42ba73d03e58dce5d0f76d3)
(cherry picked from commit fc9aab94)