tests/migration: Print some debug on bad status

We're seeing occasional asserts in 'wait_for_migraiton_fail', that
I can't reliably reproduce, and where the cores don't have any useful
state.  Print the 'status' out, so we can see which unexpected state
we're ending up in.

Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Message-Id: <20191108104307.125020-1-dgilbert@redhat.com>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>

tests/migration-test.c

@@ -899,8 +899,13 @@ static void wait_for_migration_fail(QTestState *from, bool allow_active)
 
     do {
         status = migrate_query_status(from);
-        g_assert(!strcmp(status, "setup") || !strcmp(status, "failed") ||
-                 (allow_active && !strcmp(status, "active")));
+        bool result = !strcmp(status, "setup") || !strcmp(status, "failed") ||
+                 (allow_active && !strcmp(status, "active"));
+        if (!result) {
+            fprintf(stderr, "%s: unexpected status status=%s allow_active=%d\n",
+                    __func__, status, allow_active);
+        }
+        g_assert(result);
         failed = !strcmp(status, "failed");
         g_free(status);
     } while (!failed);