tests: make sure that DispVM service call receive EOF

Even when the test fails. Otherwise the DispVM will stay alive.

tests/vm_qrexec_gui.py

@@ -837,7 +837,7 @@ class TC_20_DispVMMixin(qubes.tests.SystemTestsMixin):
         dispvm = self.qc[max_qid]
         self.assertNotEqual(dispvm.qid, 0, "DispVM not found in qubes.xml")
         self.assertTrue(dispvm.is_running())
-
+        try:
             window_title = 'user@%s' % (dispvm.template.name + "-dvm")
             p.stdin.write("gnome-terminal -e "
                           "\"sh -s -c 'echo \\\"\033]0;{}\007\\\"'\"\n".
@@ -864,7 +864,7 @@ class TC_20_DispVMMixin(qubes.tests.SystemTestsMixin):
                     self.fail("Timeout while waiting for gnome-terminal "
                               "termination")
                 time.sleep(0.1)
-
+        finally:
             p.stdin.close()
 
         wait_count = 0