auto-t: delay rekeys in extended key ID test

The test was rekeying in a loop which ends up confusing hostapd
depending on the timing of when it gets the REKEY command and any
responses from IWD. UML seemed to handle this fine but not QEMU.

Instead delay the rekey a bit to allow it to fully complete before
sending another.

autotests/testWPA2-ext-key-id/connection_test.py

@@ -50,6 +50,8 @@ class Test(unittest.TestCase):
             testutil.test_iface_operstate()
             testutil.test_ifaces_connected()
 
+            wd.wait(0.5)
+
         device.disconnect()
 
         condition = 'not obj.connected'