main: Add artificial delay before starting daemon

The IIO core, or the HID layer for HID sensor hubs, seems not
to like being poked straight after waking up, so add an
artificial delay during startup.

This is similar to the work-arounds doing the rounds in the
iio-sensor-proxy issues that switch the service type to idle
which would add a delay of up to 5 seconds by waiting for
other daemons to have finished startup.

This will need a real fix in the kernel at some point.

src/iio-sensor-proxy.c

@@ -768,6 +768,8 @@ int main (int argc, char **argv)
 
 	/* g_setenv ("G_MESSAGES_DEBUG", "all", TRUE); */
 
+	g_usleep (G_USEC_PER_SEC * 3);
+
 	data = g_new0 (SensorData, 1);
 	data->previous_orientation = ORIENTATION_UNDEFINED;
 	data->uses_lux = TRUE;