auto-t: scan as many times as needed to find networks

Certain autotests coupled with slower test machines can result in lost
beacons and "Network not found" errors. In attempt to help with this
the test can just rescan (30 seconds max) until the network is found.

autotests/util/iwd.py

@@ -489,16 +489,24 @@ class Device(IWDDBusAbstract):
            network wasn't found. If the network is not found an exception is
            raised, this removes the need to extra asserts in autotests.
         '''
-        ordered_networks = self.get_ordered_networks(scan_if_needed)
+        def wait_for_network(self, network, scan_if_needed):
+            networks = self.get_ordered_networks(scan_if_needed)
 
-        if not ordered_networks:
-            raise Exception('Network %s not found' % network)
+            if not networks:
+                # No point in continuing if we aren't going to re-scan
+                if not scan_if_needed:
+                    raise Exception("Network %s not found" % network)
 
-        for n in ordered_networks:
-            if n.name == network:
-                return n
+                return False
 
-        raise Exception('Network %s not found' % network)
+            for n in networks:
+                if n.name == network:
+                    return n
+
+            return False
+
+        return ctx.non_block_wait(wait_for_network, 30, self, network, scan_if_needed,
+                                    exception=Exception("Network %s not found" % network))
 
     def wps_push_button(self):
         self._wps_manager.PushButton(dbus_interface=IWD_WSC_INTERFACE,