wpaspy: Be a bit more careful on detaching the control interface

Check that the client socket is still open before trying to detach the
control interface to avoid undesired exceptions on cleanup paths on
unexpected errors due to the socket getting closed.

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

wpaspy/wpaspy.py

@@ -113,6 +113,9 @@ class Ctrl:
     def detach(self):
         if not self.attached:
             return None
+        if self.s.fileno() == -1:
+            self.attached = False
+            return None
         while self.pending():
             ev = self.recv()
         res = self.request("DETACH")