autotest: pass missing association parameters in network_WiFi_SuspendStress

Pass the |is_hidden| and |security_config| parameters to the
AssociationParameters constructor in network_WiFi_SuspendStress so that
the DUT will properly connect to the AP when it is configured as a hidden
network or with WEP or WPA2 security enabled.

Also:
  - Fix a type in wifi_proxy.py
  - Add an argument name specifier in a function call in
    network_WiFi_SuspendStress.py

BUG=chromium:468522
TEST=Run network_WiFi_SuspendStress.WEP40, network_WiFi_SuspendStress.WPA2,
     network_WiFi_SuspendStress.Hidden using test_that and verify that they
     pass.

Change-Id: Id02839c7aa13c6be636a2ee5c733d7f64216de16
Reviewed-on: https://chromium-review.googlesource.com/262961
Trybot-Ready: Samuel Tan <samueltan@chromium.org>
Tested-by: Samuel Tan <samueltan@chromium.org>
Reviewed-by: Christopher Wiley <wiley@chromium.org>
Commit-Queue: Samuel Tan <samueltan@chromium.org>
2 files changed