fixup! xapi.conf: introduce test_open

This commit got split between the 3 epoll PRs, and the Makefile part got missed:
f4baafa ("Test for absence of select: introduce open_1024 in tests")

The build still worked locally because I have ulimit > 1024 (and apparently in the CI too?),
but it failed in Koji where we had a 1024 limit.

Signed-off-by: Edwin Török <edwin.torok@cloud.com>

Makefile

@@ -62,6 +62,7 @@ TEST_TIMEOUT=600
 TEST_TIMEOUT2=1200
 test:
 	ulimit -S -t $(TEST_TIMEOUT); \
+	ulimit -n 2048;
 	 (sleep $(TEST_TIMEOUT) && ps -ewwlyF --forest)& \
 	 PSTREE_SLEEP_PID=$$!; \
 	 trap "kill $${PSTREE_SLEEP_PID}" INT TERM EXIT; \