various tx5 fixes

[neonphog]

• support multiple iceservers blocks in turn_doctor
• account for possibility of multiple Open events on data channel in turn-stress
• fix multiple sodoken versions creeping in, and add a ci check to prevent that

[steveej]

i ran this successfully

  ( set -e;
    for i in `seq 1 10`; do
      cargo run --example turn-stress turn.infra.holochain.org 443 test test;
      cargo run --example turn_doctor wss://signal.infra.holochain.org;
    done
    echo success
  )