Fix direct UDP communciation with pre-relaying 1.1 nodes.

Fix direct UDP communciation with pre-relaying 1.1 nodes.

try_tx_sptps() gives up on UDP communication if the recipient doesn't
support relaying. This is too restrictive - we only need the other node
to support relaying if we actually want to relay through them. If the
packet is sent directly, it's fine to send it to an old pre-node-IDs
tinc-1.1 node.