Ensure synchronized access to the H2Connection
Ensure synchronized access to the H2Connection

- introduce _LockedH2Connection that wraps the
  h2.connection.H2Connection

- use it to prevent unsynchronized access to the connection

fredthomsen/hyper,plucury/hyper,lawnmowerlatte/hyper,Lukasa/hyper,Lukasa/hyper,fredthomsen/hyper,lawnmowerlatte/hyper,plucury/hyper