remote/exporter: reduce update delay

To reduce the waiting time for USB devices like fastboot or serial in
test suites, call poll slightly more often.

Signed-off-by: Jan Luebbe <jlu@pengutronix.de>

labgrid/remote/exporter.py

@@ -463,7 +463,7 @@ async def _poll_step(self):
     async def poll(self):
         while True:
             try:
-                await asyncio.sleep(1.0)
+                await asyncio.sleep(0.25)
                 await self._poll_step()
             except asyncio.CancelledError:
                 break