auto-t: disable update_config for testDPP

update_config=1 lets wpa_supplicant write config changes
to the config file. In the real world this is what you want
so your DPP credentials are persistant. But for testing this
is not correct since multiple tests use the same config file
and expect it to be pristine.

Occationally wpa_supplicant was connecting to the AP without
running DPP because the config already had the network
credentials.

autotests/testDPP/wpas.conf

@@ -1,5 +1,5 @@
 ctrl_interface=/tmp/rad1-p2p-wpas
 
-update_config=1
+update_config=0
 pmf=2
 dpp_config_processing=2