migration: Clear fd also in error cases

Not clearing the fd and closing the file makes qemu spin using 100%CPU
after incoming migration error.

See for instance bug:
https://bugzilla.redhat.com/show_bug.cgi?id=518032

Signed-off-by: Juan Quintela <quintela@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
diff --git a/migration-exec.c b/migration-exec.c
index 3edc026..6ff8449 100644
--- a/migration-exec.c
+++ b/migration-exec.c
@@ -120,12 +120,12 @@
     }
     qemu_announce_self();
     DPRINTF("successfully loaded vm state\n");
-    /* we've successfully migrated, close the fd */
-    qemu_set_fd_handler2(qemu_stdio_fd(f), NULL, NULL, NULL, NULL);
+
     if (autostart)
         vm_start();
 
 err:
+    qemu_set_fd_handler2(qemu_stdio_fd(f), NULL, NULL, NULL, NULL);
     qemu_fclose(f);
 }