rfkill: fix erroneous behavior when polling the udev monitor (#6489)

Comparing udev_device_get_sysname(device) and sysname will always return
true. We need to check the device received from udev monitor instead.

Also, fd_wait_for_event() sometimes never exits. Better set a timeout
here.

(cherry picked from commit 8ec1a079)
(cherry picked from commit cd8a9ccb)
(cherry picked from commit 638c0dba)