tests: Fix rfkill testing with updated kernel

Kernel commit 14486c82612a ("rfkill: add a reason to the HW rfkill
state") added an extra byte to the end of the rfkill events and that
confused the read loop here since python tried to buffer the results
from multiple read() calls into the local buffer that then delivered the
extra octets in consecutive events. Fix this by disabling buffering for
these reads.

Signed-off-by: Jouni Malinen <jouni@codeaurora.org>

tests/hwsim/rfkill.py

@@ -126,7 +126,7 @@ class RFKill(object):
     @classmethod
     def list(cls):
         res = []
-        rfk = open('/dev/rfkill', 'rb')
+        rfk = open('/dev/rfkill', 'rb', buffering=0)
         fd = rfk.fileno()
         flgs = fcntl.fcntl(fd, fcntl.F_GETFL)
         fcntl.fcntl(fd, fcntl.F_SETFL, flgs | os.O_NONBLOCK)