totemsrp: Check size of orf_token msg

orf_token message is stored into preallocated array on endian convert
so carefully crafted malicious message can lead to crash of corosync.

Solution is to check message size beforehand.

Signed-off-by: Jan Friesse <jfriesse@redhat.com>
Reviewed-by: Christine Caulfield <ccaulfie@redhat.com>