test: make race condition on xterm close less likely

xterm is very fast on closing when application inside terminates. It is
so fast with closing on keydown event that xdotool do not manage to send
keyup event, resulting in xdotool crash. Add a little more time for
that.

qubes/tests/integ/dispvm.py

@@ -147,8 +147,11 @@ class TC_20_DispVMMixin(object):
             self.assertTrue(dispvm.is_running())
             try:
                 window_title = 'user@%s' % (dispvm.name,)
+                # close xterm on Return, but after short delay, to allow
+                # xdotool to send also keyup event
                 p.stdin.write("xterm -e "
-                    "\"sh -c 'echo \\\"\033]0;{}\007\\\";read x;'\"\n".
+                    "\"sh -c 'echo \\\"\033]0;{}\007\\\";read x;"
+                              "sleep 0.1;'\"\n".
                     format(window_title).encode())
                 self.loop.run_until_complete(p.stdin.drain())
                 self.wait_for_window(window_title)