tests: Fix schema parser test for in-tree build

Commit 4f193e3 added the test, but screwed up in-tree builds
(SRCDIR=.): the tests's output overwrites the expected output, and is
thus compared to itself.

Cc: qemu-stable@nongnu.org
Reported-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Andreas Färber <afaerber@suse.de>
Reviewed-by: Laszlo Ersek <lersek@redhat.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>
diff --git a/tests/.gitignore b/tests/.gitignore
index f94ce04..425757c 100644
--- a/tests/.gitignore
+++ b/tests/.gitignore
@@ -23,3 +23,4 @@
 test-x86-cpuid
 test-xbzrle
 *-test
+qapi-schema/*.test.*