Change attenuated chain encoding in Wifi sensitivity tests.

This CL changes the way Wifi sensitivity test encode attenuated chains
to better support OTA test cases where antennas are connected to the AP
throught multiple attenuator ports.

Test: Done
Bug: None

Change-Id: I2c25e86b9d5cce1a51ecd7c2d76b571fe983ab35
Signed-off-by: Omar El Ayach <oelayach@google.com>
diff --git a/acts/tests/google/wifi/WifiSensitivityTest.py b/acts/tests/google/wifi/WifiSensitivityTest.py
index a92cf21..6eff2d8 100644
--- a/acts/tests/google/wifi/WifiSensitivityTest.py
+++ b/acts/tests/google/wifi/WifiSensitivityTest.py
@@ -446,7 +446,9 @@
             testcase_params['attenuated_chain'] = 'DUT-Chain-{}'.format(
                 1 if testcase_params['chain_mask'] == '0' else 0)
         else:
-            testcase_params['attenuated_chain'] = None
+            # Set attenuated chain to -1. Do not set to None as this will be
+            # compared to RF chain map which may include None
+            testcase_params['attenuated_chain'] = -1
 
         self.testclass_params[
             'range_ping_loss_threshold'] = 100 - self.testclass_params[