Correctly check connection and channel states during handshakes

[benluelo]

We do not currently check whether a channel is open or not while processing channel and connection handshakes. This can result in double submitting handshake datagrams, which will error. These states should be asserted in the transaction batch plugin (and perhaps elsewhere?) to ensure that the stored value is the same as the expected value (i.e. on open init, the stored state is open, etc)