zdtm.py: use --status-fd instead --daemon

It works faster and allows to check exit codes.

travis-ci: success for series starting with [1/2] page-server: don't return a server pid from page-server
Signed-off-by: Andrei Vagin <avagin@virtuozzo.com>
Signed-off-by: Pavel Emelyanov <xemul@virtuozzo.com>

test/zdtm.py

@@ -963,6 +963,12 @@ class criu:
 			if ret:
 				raise test_fail_exc("criu lazy-pages exited with %s" % ret)
 
+		if self.__page_server_p:
+			ret = self.__page_server_p.wait()
+			self.__page_server_p = None
+			if ret:
+				raise test_fail_exc("criu page-server exited with %s" % ret)
+
 		if self.__leave_stopped:
 			pstree_check_stopped(self.__test.getpid())
 			pstree_signal(self.__test.getpid(), signal.SIGCONT)