Always process them within a short time.  Even though waiting a little
is useful, it is not okay to delay e.g. qemu_opts_del forever.

Reviewed-by: Michael Roth <mdroth@linux.vnet.ibm.com>
Tested-by: Michael Roth <mdroth@linux.vnet.ibm.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>