cpu-gather: Ignore shutdown messages from qemu

Signed-off-by: Tim Wiederhake <twiederh@redhat.com>
Reviewed-by: Michal Privoznik <mprivozn@redhat.com>

tests/cputestdata/cpu-gather.py

@@ -98,6 +98,8 @@ def call_qemu(qemu, qmp_cmds):
         response = json.loads(line)
         if "return" in response and not response["return"]:
             continue
+        if response.get("event") == "SHUTDOWN":
+            continue
         yield response