Batches submitted via REST API during genesis are lost

[peterschwarz]

When a batch is submitted via the REST API to a validator that is processing the genesis block, it will be lost.

Steps to reproduce:

1. Create a genesis block with at least one sawtooth settings transaction
2. Start a validator process
3. Start a REST API process
4. Submit an intkey transaction (via intkey load, for example).
5. Start {{tp_settings}}
6. Start {{tp_intkey_python}}

At this point, the genesis block will be created, but the intkey transaction(s) will not be processed.

To fix this, either:

• the batch should be preserved in a pending queue (which would require journal being active)
• do not accept client messages until the genesis block is complete (probably the most desirable)

(Duplicated by https://jira.hyperledger.org/browse/STL-508)