Add network connectivity check

Add a more general check that pings a network host rather than checking
the status of dumpsys wifi. This is because not all devices are
connected via wifi.

wlauto/workloads/multiapp/__init__.py

@@ -124,6 +124,9 @@ class Multiapp(AndroidUiAutoBenchmark):
     def initialize(self, context):
         super(Multiapp, self).initialize(context)
 
+        if not self.device.is_network_connected():
+            raise DeviceError('Network is not connected for device {}'.format(self.device.name))
+
         # Check for workload dependencies before proceeding
         jpeg_files = [entry for entry in os.listdir(self.dependencies_directory) if entry.endswith(".jpg")]