[fuchsia][wlan] Use sta_addr instead of mac_addr for QueryIfaceResponse

The fuchsia.wlan.device.service/QueryIfaceResponse was modified
in https://fuchsia-review.googlesource.com/c/fuchsia/+/562146
to use the field name `sta_addr` instead of `mac_addr`. The
field is now referred to properly in wlan_controller.py.

Bug: None
Test: WlanPhyComplianceABGTest:test_associate_11b_only_short_preamble

Change-Id: Ic21d16ec4197814f380035423af50d224a77a28a
diff --git a/acts/framework/acts/controllers/fuchsia_lib/lib_controllers/wlan_controller.py b/acts/framework/acts/controllers/fuchsia_lib/lib_controllers/wlan_controller.py
index 005c332..0d3e255 100644
--- a/acts/framework/acts/controllers/fuchsia_lib/lib_controllers/wlan_controller.py
+++ b/acts/framework/acts/controllers/fuchsia_lib/lib_controllers/wlan_controller.py
@@ -89,7 +89,7 @@
                     'Failed to query wlan iface id %s: %s' %
                     (id, response['error']))
             wlan_ifaces_by_mac[utils.mac_address_list_to_str(
-                response['result']['mac_addr'])] = response['result']
+                response['result']['sta_addr'])] = response['result']
 
         # Use mac addresses to query the interfaces from the netstack view,
         # which allows us to suppliment the interface information with the name,