test: Make http server's UntilEvent instance usable by tests.

Do not wait forever so test does not block.
Always clear event after it occurred.
Also, ensure itsUntilEvent behaviour is to raise so server actually stops
in _stopServer.

caucase/test.py

@@ -201,7 +201,8 @@ class UntilEvent(object):
     now = datetime.datetime.utcnow()
     while now < deadline:
       self._wait_event.set()
-      assert self._event.wait()
+      assert self._event.wait(10)
+      self._event.clear()
       if self._action is ON_EVENT_EXPIRE:
         now = deadline
       else:
@@ -294,7 +295,7 @@ class CaucaseTest(unittest.TestCase):
     """
     Start caucased server
     """
-    self._server_event.clear()
+    self._server_until = until = UntilEvent(self._server_event)
     self._server = server = threading.Thread(
       target=http.main,
       kwargs={
@@ -305,7 +306,7 @@ class CaucaseTest(unittest.TestCase):
           #'--threshold', '31',
           #'--key-len', '2048',
         ) + argv,
-        'until': UntilEvent(self._server_event),
+        'until': until,
       }
     )
     server.daemon = True
@@ -327,6 +328,7 @@ class CaucaseTest(unittest.TestCase):
     Stop a running caucased server
     """
     server = self._server
+    self._server_until.action = ON_EVENT_RAISE
     self._server_event.set()
     server.join(2)
     if server.is_alive(): # pragma: no cover